Hey guys, like many of you, I've rooted my HTC Thunderbolt. (Before I'd even had it for 24 hours, haha. Whatever, I need my custom fonts and Titanium Backup...)
As I know was the case for me and many of you, the Superuser app was disturbingly wonky — well, no more, as rmk40 on XDA has posted his modification of the Superuser app that smooths everything out. No more FCs — it has been working for me flawlessly. (It was due to the fact that his binary was being provided with the rooted ROMs without the matching app.)
Check it out on XDA, he explains it.
XDA - Working Superuser for TB Sense