I use Roundcube mail from time to time, but faced some errors or weird behaviour regularly. I therefore decided to re-install the latest stable version, which is 0.3 at the time of this writing.

It was quite easy the last time, so I expected having it done in minutes. I failed!! I regularly got empty pages and wasn't able to run through the installer... *sigh* After a while of debugging the code, I got the idea that eAccelerator might cause the trouble and added

php_admin_value eaccelerator.enable 0

to my Apache's vhost settings.