Good thinking, YouCanToo!
When you removed the pkgcache files in /var/cache/apt did you remove the archives folder, too? If so, go to /var/cache/apt, right click in the directory and choose New > Folder. Name it archives. (all lower case characters) Next, right click it and choose Properties; click the permissions tab and make sure that the execute boxes are checked.
Do the same for the partial folder in /var/lib/apt/lists, if you deleted it.