Unable to remove files within ./../cache/

I get this error at the end of the conversion process:
"Unable to remove files within ./../cache/. Please check directory permissions."

It happens after I get all the reports about inserting the new data from the old phpBB2.0.x to phpBB3.0.
After I see step 27 of 27 complete....

I tried to change all the permissions for the cache folder, for the files in it and for the whole phpBB3.0 folder... but nothing works.

I guess I finished the whole conversion process and the only thing missing is to clean the cache.... I can do it manualy but not sure if this is right...

Any ideas?