I just installed 3.0.2 on my ubuntu 8.04 LTS and faced similar problem. It worked fine in another server with 188.8.131.52 on ubuntu 8.04 LTS.
Anyway, I followed the guide here and enabled verbose logging on my pureftp. Then saw some error on ispconfig trying to access mysql using 'ispconfig'@'localhost'. Then I check in my mysql privileges and only see ispconfig with 127.0.0.1 only. Then I changed that 127.0.0.1 to localhost and it is working now.
But my question is, will this cause any problem on other ispconfig script that might try to access using 'ispconfig'@'localhost'?