After updating to FF13, but also after a round of malware clearing, Adobe Acrobat Reader plugin does not activate. Upon clicking on a pdf link, the "What should Firefox do with this file" dialog appears. Mimetypes.pdf and pluginreg.dat were deleted with no fix, so uninstalled and reinstalled Reader 10 and deleted both files again. Still the same behavior. I have both Acrobat 8.0 and Reader 10 installed. I also tried deleting the nppdf32.dll from Program Files/Acrobat 8.0.