One of your add-ons might be the culprit. Try running Firefox in Use Troubleshoot Mode in Firefox with all add-ons disabled. If that solves the problem, see Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems and possibly Troubleshoot issues with plugins like Flash or Java to fix common Firefox problems

I had the cursor disappear except when it was moving, in Firefox under Windows XP. It resolved itself after I shut down Windows XP and rebooted, and then restarted Firefox. If you have not already done, so, try rebooting and restarting Firefox. That seems to be the simplest first step.

We have encountered a problem of intermittent cursor flickering in Firefox 3.6.8 (.NET CLR 3.5.30729) running in Windows XP Media Edition (v 5.1 build 2600 service pack 3) on a HP Pavilion Pentium machine. I have checked it by running the Mouse diagnostic through the Control Panel, which reports the mouse is working properly. I switched the mouse out with an old one, and encountered the same flicker. This flicker does not occur with the Windows Desktop, Control Panel, MSWorks Word Processor, or Google Chrome. I had those windows open at the same time as Firefox, and in going from one of them to the Firefox window and back again, the flicker started and stopped. This problem is intermittent, and only occurs for short periods of time (several hours), from time to time. It was first complained about to me by my wife about Aug. 7, 2010. I am also running 3.6.8 (.NET CLR 3.5.30729) in XT Media Edition on a Core 2 Duo HP Pavilion, and do not observe the problem. More details available if necessary. Wilber_d_w@windstream.net

Never saw this problem until today, first on Facebook, then on these Mozilla support pages. I had one Firefox window with multiple FB and Mozilla tabs open.

Here's my observations: On the FB and Mozilla pages, the cursor (arrow/hand) acted identical and as described here, would disappear after 2-3 seconds of inactivity or non-motion, then instantly reappear with mouse movement or key strike but only momentarily if no further motion/action occurred. Interestingly, I also had one FoxNews tab (actually FoxNewsInsider) open, and observed slightly different activity. The Cursor/hand would disappear as described above, but instead of staying invisible, it flashed on /off for what appeared to be <1 second on then <1 second off, until mouse movement or key strike. Now, here's the really interesting part ... When I opened a second FoxNewsInsider tab, the problem corrected itself with no direct action on my part to resolve the issue. I was going to close all tabs, then Firefox and perform the system reboot to correct this annoyance ... but, still have not seen the problem.

Okay, I'm not going to say viewing FoxNewsInsider webpages not only provides one perspective on news, and the added benefit of fixing cursor/hand problems .. but maybe there's some to being well informed ... Sorry folks, couldn't resist ...  :) I will be watching for the disappearing cursor issue again, and will reply here with any updates or changes in my observations.