Same problem here.
I have got a new device yesterday. First step was to update to PR1.1.

After that I've tried to import the root certificate of cacert.org. This was sucessful, but everytime I tried to access a HTTPS-side (with cacert-Certificate) gives an error message (...uses an invalid security certificate.).

Restart of browser and reboot of phone doesn't help.
It sounds like this problem (before PR1.1):
https://bugs.maemo.org/show_bug.cgi?id=6211

But now also a restart doesn't help. I can't find an entry in Bugzilla.
Does anybody already added a bug report?