Are there any plugins like Flash running on that website when this happens?

• http://www.marktplaats.nl/

Do you otherwise have problems with Flash?

You can check for problems with current Flash plugin versions and try these:

• disable a possible RealPlayer Browser Record Plugin extension for Firefox and update the RealPlayer if installed
• disable protected mode in Flash 11.3 and later
• disable hardware acceleration in the Flash plugin

• http://kb.mozillazine.org/Flash#Troubleshooting

Thanks for your reply,

I have tried with all the plugins disabled, no difference. Upgraded and downgraded FF, updated Graphic Driver, upgrade and downgraded Adobe Flash, no result.

So, Safe Mode doesn't have any effect?

Try to create a new profile as a test to check if your current profile is causing the problems.

See "Creating a profile":

• https://support.mozilla.org/kb/profile-manager-create-and-remove-firefox-profiles
• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Profile_issues

If the new profile works then you can transfer some files from an existing profile to the new profile, but be careful not to copy corrupted files.

• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

Try to boot the computer in Windows Safe mode with network support (press F8 on the boot screen) as a test to see if that helps.