I haven't pinned down the sequence of events but I notice after awhile the clearclick line on the plugins tab is missing. Reset and restarted doesn't bring the line back. Reinstalling Noscript does bring the line back. This might be a Minefield issue.
CheckPlaces 1.4.1
CS Lite 1.4
Download Manager Tweak 0.8.4
Extended Statusbar 1.5.4
Firekeeper 0.3.1
Nightly Tester Tools 2.0.2
NoScript 1.9.5.6
Surf Canyon - Search Engine Assistant 2.0.5
User Agent Switcher 0.7.2
WOT 20090414
Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2a1pre) Gecko/20090709 Minefield/3.6a1pre ID:20090709091211
Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2a1pre) Gecko/20090709 Minefield/3.6a1pre