If you’re a .Mac member who’s been plagued by the “Local iDisk is the wrong size” error, I have a fix for you.
That fix is to turn off the Create a Local copy of Your iDisk option and then switch it back on again. This appears to clear iDisk’s confusion.
To set about it, launch System Preferences and click the .Mac option. In the resulting window uncheck Create a Local copy of Your iDisk. Quit System Preferences and click Turn Off Local iDisk in the sheet that appears. You’ll be presented with a message that reads The iDisk on Your Computer Has Been Disabled.
Relaunch System Preferences and re-enable the Create a Local Copy of Your iDisk option and the “wrong size” error should disappear.