Kbase Article of the Week: MobileMe: Unable to Select Items for Upload to MobileMe iDisk or MobileMe Gallery via Web Browser in Microsoft Windows →

Apple Support:

The upload utility for MobileMe Gallery and MobileMe iDisk may not display files correctly when accessed from a web browser in Microsoft Windows. In this case, folders that contain files may appear to be empty.

This issue may occur in any supported Windows web browser, such as Safari for Windows, Firefox, and/or Internet Explorer.

The fix in the article includes this glorious screenshot:

MobileMe iDisk in XP