To track down the cause of the crash while generating thumbnails (which may be due to a 3rd party component), see these two guides:
[ul][li]Crash, exit or high CPU when viewing certain directories[/li]
[li]Crash dumps for bug reports[/li][/ul]
You can reset the colors to the defaults by going to Preferences / Display / Colors and Fonts and using File / Reset Page To Defaults.
