Thanks for your help so far Philba, I really appreciate it.
I downloaded Viewmate and opened up the Gerber (cmp file). The contents didn't make much sense to me at first, but after a while I found the aperture 10 error (0.0059).
I changed it to 0.007 and zipped up all files and submitted it. The first check done but batchpcb succeeded, no aperture to thin errors anymore.
After a few minutes I received an email stating that DRC errors (clearance) were found.
When I checked the attached images, I found that they were all on the 4 inside corners of the atmega168 mlf32 SMD pads, see image:
There is nothing I can do about this, right? I am a noob in doing this electronics stuff... I am not too much looking forward into making a new footprint...
Edit: I should add that I have used a clearance of 7 mil, I think I read somewhere that user 'busonerd' (?) stated that allthough they promote the batchpcb service with 8mil spacing/tracing, the bot allows for down to 6.9mil. Please correct me if I am wrong