I get the following error when trying to automatically download and install corecommerce 1.5 through my dashboard

The following errors occurred when attempting to process your request:
Unable to backup old package directory to /home/mob2you/domains/mobiletoyou.com/public_html/files/trash


So i tried chmodded files/trash to read/write... which helped nothing.... Should I install 1.5 just as I originally installed 1.1? with a manual upload, and overwrite 1.1