Lost PDF icons in Explorer

This is more of an annoyance than a problem, but suddenly all the Explorer
icons for PDF files have changed from the Acrobat icon I've always seen to
generic Windows icons for unknown file types. The extension is still
associated with Acrobat Reader, and double clicking a file opens it
correctly in Acrobat, but the icons remain incorrect. I've tried deleting
the iconcache so it could rebuild, and changing the association to another
app and then back again, to no avail. PDF files appear to be the only ones
effected.

Any suggestions?

Buddha