755 technically should work as long as the folders are owned by the php process (if I remember right). You may also have other safe mode type restrictions in place that can prevent the uploading of files (thats why the gallery aspect was so important for release). You may be best contacting your host to enquire about the problem. You may also want to double check that your paths in the settings are acurate.
yoyo - Ive wondered about that. My guess is that I dont think there is a 'minimum' as much as a 'request' to get into the premium forum. To be honest, Im not overly bothered about it. Some things would be easier if GAS had a forum - but not many. I kind of like having a 1,500 thread mack... it makes me feel like all manly and stuff