I often get black bars that appear on my WLM client.  This happens a lot when I am working with the application.  It usually appears when I try to resize a window or when i have it open for awhile.  I usually can close out of it and then it would come back up without issues.  However, it would happen about a half dozen times in a typical 8 hr work day.  I've attached a photo of what I mean by black bars.  I am using Windows 7 64bit and Windows Live Mail 2012.

Any suggestions on how to resolve this issue?