advanced-cache.php problems on upgrade

When trying to upgrade I’ve been getting this message:

Warning: require(/there/is/a/path/here/blog/wp-content/advanced-cache.php) [function.require]: failed to open stream: No such file or directory in /there/is/a/path/here/blog/blog/wp-settings.php on line 69
Fatal error: require() [function.require]: Failed opening required '/there/is/a/path/here/blog/wp-content/advanced-cache.php' (include_path='.:/usr/local/php5/lib/php') in /there/is/a/path/here/blog/blog/wp-settings.php on line 69

Last time (when trying to upgrade to 2.0.5) I just re-uploaded my 2.0.4 backup, but this time I tried to comment out the mentioned lines and 2.0.6 seems to be running fine without them, so I’m just curious about what caused the problem and how to prevent it from occurring again.

I had wp-cache installed once, but it has just been sitting inactive in my plugins folder since then… but maybe it could be a part of the problem even though it had been deactivated?