Cannot use apostrophes in posts in Guestbook?

Hi:

Hope someone can help. For some reason, any entry into the guestbook that contains an apostrophe ('), cannot be edited in the admin for the guestbook. Any attempts to edit the entry result in a MySQL error 1064 syntax error. If the apostrophe is removed when editing, the entry can be edited.

Just an FYI, but I notice that in the demo guestbook, there are entries with apostrophes, and am wondering if you've experienced the same problem?