1)  Personal icons (Documents and so on) randomly reverting to the Windows defaults.

2)  Other folders, such as subdirectories in Pictures, randomly reverting to the defaults when browsing for a file to open from software such as Photoshop.

3)  Applying new icons to filetypes MP3 and WMA makes zero difference.

4)  Everytime any of these things happen, a rebuild is necessary, which lasts a whole few days before random icons start reverting again.

Running on an unremarkable installation of Windows 7.