Rayzz,
That's the same IP that attacked us. As I stated earlier we upgraded to the latest release. What I neglected to mention was that we nuked the class C license the ip originated from on our firewall, not the best preventive measure I admit, but seeing as you posted the same IP it might hold more of a chance at thwarting future attempts then I originally hoped.
I have faith in roundcube, it was, after all, listed as beta when we first started using it, and as far as I'm aware its still a beta product. I can't knock free and I still haven't seen a comparable product for the price that is so feature rich. I have been through Squirrelmail and Hastymail, and just felt home using roundcube.