Ohhhhh... so THIS is why I can't root. Bugger!
I recently SBF'd using the leaked GB SBF (big thanks for that, made life a lot easier), and was spending the past 30 mins or so wondering why every root tool I downloaded wasn't working. The more you know!
I hope a new root exploit is found soon...
EDIT: Apparently there is no exploit as of now, but it is possible to preserve an existing root via an app called RootKeeper (on the market). There's a post about it on the first page of this thread.
...glad I didn't get to re-installing all my apps... time to SBF again... bollocks.