I looked today and npviewer was using 100% of the CPU but Iceweasel wasn't running. Here's another message (repeated many times) from the .xsessio n-errors that may not have appeared in the last listing:
*** NSPluginViewer *** ERROR: NPN_GetURLNotify() invoke: Connection closed -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]