I've been running into this issues on and off for a while too. On the best days I can login to bugzilla.o.o, and on worse days, not even in bugzilla.s.c. Can't say much of what's going on though. When the issue occurs, I prompt my username and password, hit enter and the forms get cleared. And it fails to show any message of what went wrong. If anyone has any idea on how to debug this, please speak up.