I installed the IE7 beta on my computer earlier this week, and it *seemed* (on first glance) to be working fine alongside Firefox. But then I started noticing strangeness. My computer auto-rebooted several times due to failure of \WINDOWS\system32\lsass.exe, in one case involving the wdigest.dll module: this might be an indicator of several varieties of virus, but my machine scanned clean with the latest version of Avast, which is usually pretty reliable.
Then I noticed that clicking on an embedded http link in an email message no longer opened a browser window: instead, it opened a file system explorer window. I ran Windows’ “Set Program Access and Defaults” utility to re-confirm that Firefox was my primary browser- that didn’t seem to help. I re-installed Firefox- that didn’t improve things either. Finally, I used the wonderful Windows System Restore feature and reverted back to before I installed IE7. Everything seems back to normal again- I’ll have to wait for 24 hours to see if I continue to see problems with lsass or not. When I switched to using IE7 as my default browser, http links worked fine- I didn’t wait long enough to see if the lsass.exe errors repeated themselves.
Netting it out, my machine (Windows XP 64; AMD Athlon processor; 2 GB of RAM, all current available Windows patches, Avast antivirus, Microsoft AntiSpyware) running Firefox 18.104.22.168 appears to have had problems with IE7 Beta 2. I suspect that if I had run with just IE7 I wouldn’t have had these problems. Alternately, I could have some new virus on my machine that Avast isn’t detecting- but that seems somewhat unlikely.
For now, I’m running without IE7. I’ll check it out again later.