I've had a stable 1.0.8. when i tried to upgrade, i couldn't log in anymore.
I tried reseting my pass, and the same problem: I try to login, it says that pass security has been upgraded and prompts me to enter my pass again. I do that and ta-daam: white screen.
Help! :'(
try deleting your cookies and cache, that may help.
What is the address of the page which makes a white screen?
You can also try this:
Having problems with mod_security? (http://www.simplemachines.org/community/index.php?topic=34270.0)