I recently upgraded from 0.8.1 to 0.8.4, and now, in the rc error log I can see:
[17-Jan-2013 08:37:59] MDB2 Error: not found (-4): no RDBMS driver specified
[17-Jan-2013 08:37:59 +0100]: DB Error: no RDBMS driver specified in /aplicacions/webmail/roundcube-0.8/program/include/rcube_mdb2.php on line 107 (POST /rcube/?_task=login&_action=login)
I ran the upgrade script from the 0.8.4 folder, setting as target my running 0.8.1 folder...
Roundcube is running fine (or at least it seems to me), but this is a bit suspicious...
Are you using any plugins, is the problem repeatable?
I tried to disable all my plugins one by one and it seems that is related to plugin_manager...
I'll try to ask at myroundcube forums to see if we find where is the problem...
Thanks for the clue!
Be sure that there is no 'suspicous' code in plugin_manager. We have complaints about this error but we can't reproduce/locate it. If you have some heads up, please contact me: myroundcube [at] mail4us [dot] net. Thank you!