Check out my post here
There are two BB KB articles that "sort of" cover the issue.
Bottom line, there are two problems with CICAL service books, calendar alerts and the 8830. RIM lists both issues as "ongoing and forwarded to our engineering department." I'm hoping they release a fix soon.
You can try re-sending your service books and then deleting all but one of the CICAL service books, try to sync and check to see if you are still getting your calendar alerts.
(oh yea, do yourself a huge favor and get missing sync for blackberry - well worth the price of admission.)