In your Program Files folder, navigate to the Mozilla Firefox folder, the "Update" folder. If there is a folder in it called \0\ or \1\, delete it.

Could not find an 'update' or 'upgrade' folder anywhere under \program files\mozilla firefox\.

Found one under user profile. Deleting that did not fix it.

I do see lots of files with .moz-delete and .moz-upgrade in \mozilla firefox\.

I'm not sure where the cause of the problem is. Try uninstalling Firefox through the Windows control panel. Then reboot your computer. Then delete the C:\Program Files\Mozilla Firefox\ folder. Then try installing the latest version.

un-install / re-install solved the 'reboot' issue, but then left me with a situation that when Firefox starts all i see is a small window that contains just a bit of text along the lines of :

Looks like the forum won't let me include the exact text of the error message so half my previous post got lost. Text in the window (minus the left/right brackets).

window id="mainWindow"

safe made resulted in something like :

safemode id="safemodedialog"

(sorry, don't have exact text, FF un-installed on the PC in question)

Your Firefox settings and info are kept in a folder separate from the Firefox program, called your profile folder. Try creating a test profile, to see if the problem still occurs. See Profile Manager - Create, remove or switch Firefox profiles

I seem to have the same problem - but on the way to downloading the update there were a couple of strange experiences which made me wonder whether this update was corrupted or in the worst case hacked. Lucky I have the Welsh (/cy) version of Firefox as a separate installation - Mozilla/5.0 (Windows; U; Windows NT 5.1; cy; rv:1.9.2) Gecko/20100115 Firefox/3.6 - the standard (/en) version is completely stuffed after "upgrading" to 3.6.8 - all I can get is [popup box] Setup / ! \ Your computer must be restarted to complete a previous upgrade of Firefox. Do you want to reboot now? [Yes] [No] /popup

Contextual info - in reverse order - Just in case it's relevant. I downloaded the upgrade by going to the mozilla site and using "save link as...", and then executing the saved Firefox Setup 3.6.8.exe (8,399,936 bytes). The "Do you want to reboot now?" prompt appeared but I put this off, wishing to check my mail inbox before closing down for the night (did I respond to it before shutting down? Can't honestly remember).

Before this, I had tried just clicking on the link on the Firefox upgrade prompt page which had appeared by magic in a new tab - but I aborted this when I noticed in the status line that the browser seemed to be contacting http://[some short url].jp

Before this I had followed the "see all changes in this version/ update" link and found one change listed. _Much_ earlier I had found that following that link retrieved _no_ changes, and had submitted a note querying whether this was a null update(!).

Config info OS Name Microsoft Windows XP Home Edition Version 5.1.2600 Service Pack 1 Build 2600 System Name RHIANNON System Manufacturer HP Pavilion 061 System Model DQ072A-ABU a309.uk System Type X86-based PC Processor x86 Family 15 Model 2 Stepping 9 GenuineIntel ~2400 Mhz Locale United Kingdom Hardware Abstraction Layer Version = "5.1.2600.1106 (xpsp1.020828-1920)" Time Zone GMT Daylight Time Total Physical Memory 256.00 MB Available Physical Memory 46.77 MB Total Virtual Memory 853.46 MB Available Virtual Memory 384.19 MB Page File Space 605.98 MB Page File C:\pagefile.sys

Aha - had a look at the install log, and found the following about half way along - what next??

(...)

DLL Registration

 ** ERROR Registering: C:\Program Files\Mozilla Firefox\AccessibleMarshal.dll **

Installing Localized Files (...)

Reckoning it might be some time before a response (my previous above is timed at 02:27 PST)... and reckoning that the Mozilla Firefox folder did not look too healthy (couple of fairly recent recovered file fragments, numerous -moz-delete files that look as if they're left over from the 3.7 update, etc; I thought I'd just try running the update file again. It seems to have worked(*).

The difference is that I ran it from an administrator account.

Now I'm aware that the instructions for first-time-install emphasize running install from an admin account. However I'm pretty sure at least some updates appear to have worked from a vanilla user account. If they _should_ always be run from an admin account, then could I suggest

- putting a reminder on the "update now" etc. screens
- adding a check in the updater run module, with at least a warning message! 

(*)apart from a problem with language preference - the following 404 url was emitted from a support page "search" attempt URL has two language preference tags concatenated - .../en-US/cy/... - but that's another story !

Resolved the issue by removing all trace of Firefox, un-installed, looked for folders and deleted them and removed every registry key that looked remotely related to firefox. After this the firefox installer, and indeed other installers started working nicely. Problem has not returned since.

I deleted the Mozilla Firefox folder in Program Files and downloaded the old installer (3.6.16). Installed fine then downloaded the 5.0 installer and installed with flying colors/

I don't know whether or not this has affected my scenario, I'm on Windows 7 Ultimatre, 64-bit, did a system restore. However I see no "update" foklder anywhere, nor an uninstall exe since I've already uninstalled.

system restore (xp) fixed the problem on my two machines! the update of firefox was recognized nevertheless!

Nothing simple has resolved this problem. I am not going to do a system restore or a regedit that'll most likely corrupt my system. If Mozilla/Firefox cannot sucessfully post a solution to this problem they have introduced, I (others, too) may just be better off going to use another browser. Browsers are a dime a dozen. Mozilla/Firefox deserves to lose us if they are unresponsive to our problems and needs.

You can only get such an error if there is other (security) software on your computer that is using or protecting files in the Firefox program folder (C:\Program Files\Mozilla Firefox\).

You should be able to fix this by downloading the full Firefox version and deleting the Firefox program folder and possible already downloaded files in the updates\0 folder.

• http://kb.mozillazine.org/Software_Update (Software Update not working properly)