Have you tried deleting the .dat cache file? This helps to clear up some errors that seem to occur at random after an extension is installed. Here is a link to a thread that discusses how to clear this file:
showthread.php?t=1589
If you continue to have issues with this it may be due to a corrupt configuration folder, here is a post that discusses how to rename or delete this directory to help undo any corruption that may be present:
showpost.php?p=12293&postcount=2
Please let us know if the problems persist.