odd GTK(?) problem

I recently used swaret to upgrade to Slackware 10. Everything is fine, with the exception of certain GTK applications (namely, GTK-Gnutella and Sylpheed-Claws). In these applications, odd blue lines show up between content in some windows - for example, the list of items being downloaded in GTK-Gnutella has lines separating each item, and the list of folders in Sylpheed has the same thing. I've uninstalled and reinstalled GTK+ and the like, checked dependencies, etc., but everything appears to be fine. What could be causing this?