I am using FireFox (latest version) on my PC with WinXPpro (SP3).
Previously when I clicked a link in an email (using Thunderbird) it asked if I wanted to open this link, and if I answered Yes, it opened the webpage in the browser.
Now it still asks if I want open the link, but when I say YES, I get a message saying unable to point the browser at the page. ie. It does not open the browser. The same happens if I click links in other email programs, eg MailWasher.