I run Ubuntu 10.04 on a Desktop with Avira Antivir and could use Firefox 3.x for years without problems. Since upgrading to Firefox 15.0.1 and 16.0.1 via Synaptic the message "The bookmarks and history system will not be functional because one of Firefox's files is in use by another application.Some security software can cause this problem." I tried
- to start Firefox in safe mode disabling extensions (Noscript, Ghostery, Places maintenance (hangs at executing tasks...), Ubuntufox as well as stopping the virus scanner AVGuard)
- replacing sqlite.places
- resetting firefox to factory defaults

I note the lock file in the firefox profile which appears after starting and disappears after topping firefox but the link is broken. I tried to delete it but it renews itself.

All to no avail. Any other ideas or is it time to change to Epiphany or Chromium?