1. Suddenly Firefox 8.1.1 will not start on my profile (admin). The computer thinks for 1 second and then nothing more happends. No error mess.
2. It starts and works fine at the other profile on the same computer
3. Tried to uninstall Firefox at the admin profile but during setup I get the message: "Error 1606 Could not access network location %APPDATA%\"
4. Did a deep scan on the computer with latest Avast database. No viruses found.
5. Did not install anything new in connection to when this problem arose.

I run Vista 32-bit.

Grateful for any help!

I'm confused since Firefox is currently at version 3.0.11. Where are you downloading FF from?

Good point. Firefox 3.0.11. My mistake.
I download it from: Webblsaren Firefox p svenska | Snabbare, skrare och anpassningsbar (http://sv-se.www.mozilla.com/sv-SE/)

Well here's the MS fix: You receive an "Error 1606" error message when you try to install or remove a Microsoft program (http://support.microsoft.com/kb/886549)

Let's blame Vista! My experience has been that it frequently screws up working programs. Anyway, here are two suggestions from Mozilla website.

If Firefox previously worked but suddenly doesn't start, it may be due to some corrupt data in your settings. Uninstalling and reinstalling Firefox would not fix this problem because your settings are not removed on uninstall.
To test to see if this is the problem, use the Profile Manager (http://support.mozilla.com/en-US/kb/Managing+profiles) to create a new profile. If the problem goes away, you can then move your bookmarks and other important settings into the new profile (http://support.mozilla.com/en-US/kb/Recovering+important+data+from+an+old+profile).


For Vista:


Restart your computer.
Select the Start Menu in the Windows Taskbar.
In the Search box, enter the following:
%APPDATA%
Press Enter.
From the Application Data folder, navigate to Local\VirtualStore\Program Files\Mozilla Firefox.
Delete the file xpicleanup.that.
Restart Firefox.

Good luck.

Thank you guys. I will give your suggestions a try first thing tomorrow morning and come back with what happens!

Creating a new account helped. So far so good. But all the passwords and so on are gone unfortunately.
Thanks again!

Why is your firefox profile on a network share?

Profile Manager - MozillaZine Knowledge Base (http://kb.mozillazine.org/Profile_manager)