From http://forum.beryl-project.org/viewtopic.php?f=54&t=631 :

"checkgmail is an application that sits in the notification area displaying information about your gmail inbox. when you hover over the icon, a large tooltip pops up displays the first few lines of your mail message. by each message there are various links that allow a user to archive or delete email from the popup instead of having to open firefox and visiting gmail. These links only work within metacity. When you click on a link while running beryl, the popup closees as if you clicked somewhere else on the screen. What even more odd, is that when you hover over a link it underlines properly.
Any ideas on how to remedy this?"

From the checkgmail developers (http://checkgmail.sourceforge.net/#faq):

"CheckGmail and XGL/Compiz
Sorry, but these two don't seem to like each other very much (CheckGmail still works, but you won't be able to use a lot of the nifty features). I don't have a system running XGL and can't bugfix this one myself, but from what I can tell the issue lies with incompatibilities in the Gtk2-perl modules (and more specifically the signal_connect methods) rather than my own code. Please stop reporting this issue!! At the moment there's nothing I can do about it, and anyone experiencing this problem would be better off reporting it to the Gtk2-perl developers. Thanks! :)"

--Bill Yanelli