We also get the error several times a day(PDMLink 9.1 M050, single server). We suspect that Tomcat is the culprit, because doing a quick bounce of Tomcat seems to clear it up for awhile. Our production server is a 64-bit, but we are running 32-bit Java, so on one of our dev servers we have switched to 64-bit Java to overcome the 32-bit limit of memory usage, and so far this seems to have cleared up the problem. Will report more when we swap out our production server Java to 64-bit.
Send lawyers, guns, and money...the sh!t has hit the fan!