samu2 - try editing a plugin in the Plugin Manager and then saving it without changing anything.
vonedaddy - do NOT uninstall. Just reimport the the product and check the "allow overwrite" box. If there are any errors during installation, post them.
docvader - run these queries to make sure the quote settings get reset:
Code:
DELETE FROM $TPsetting WHERE varname IN ("showquote", "ratequote", "averagethreshold", "totalthreshold")
Code:
DELETE FROM $TPdatastore WHERE title = "quote_settings"
Just replace the $TP with your table prefix first.