Carl, I have the EXACT same issue you've described and it's been with me throughout all releases of Workstation 9 (through v9.0.2). Now that I've switched to 10, it continues. The symptoms are just as you've described. My host is Win 7 Pro 64 and the guests are Win 7 Enterprise 64. If I take a client and expand it across two of my host's three displays, everything is fine until the guest's screensaver kicks in. If I unlock the screensaver, I am returned to work on the guest with both monitors but within 10-20 seconds (without fail) the second display will suddenly revert to the host's wallpaper and my guest is left showing only on the first display. However, VMware Workstation still thinks that it's running on two. If I click the monitor layout button on that guest's command bar, it shows that the current mode is Layout 2 (dual-monitor) - even though it is only utilizing the first display. This was the same in v9 - it still showed that two displays were engaged. The only remedy, as you've described, is to exit full-screen mode, re-enter full-screen mode, and then switch back to the two-display layout. This will restore all normal functionality for the guest until the next time I leave the guest OS long enough for the screensaver to activate. I tried a complete un-install and re-install of the client tools in 9.0.2 and it had no effect. When I was notified that v10 was just released I leapt at the upgrade in the hopes that, at last, there would be a resolution. However, it immediately performed the same trick when I returned from a meeting and unlocked my screensaver. And, yes, I upgrade the client tools to the latest edition that accompanied the release of Workstation 10.
I have never run any beta versions of VMware Workstation and I always install the latest versions of the program as soon as the program notifies me that an upgrade is available. I typically only have two guests active at a time - both Win 7 Enterprise 64. One guest uses two LCDs while the second guest uses the third. The host has 16GB of RAM and the troublesome guest OS has 4 GB reserved for it since this is where I perform the majority of my tasks. If it helps, the host PC uses an AMD FirePro V4900 graphics adapter. and the two LCD displays involved in this issue both connect to that card via VGA to DisplayPort adapter cables. I'm not sure what else I can tell you about it other than that this issue has been present since day one of running a Windows 7 guest inside Workstation. I'm pretty sure it started with 9.0 but it MAY have gone back as far as the last edition of 8. But I can't be sure about that. I do know, however, that none of the updates to v9 has resolved the issue nor has today's upgrade to v10.0.0. I also know that I ran in this same mode for ages using an XP Pro (32) guest and never had this issue with dual displays. Is there any suggestion for me? Should I capture any specific logs to help troubleshoot this? Thanks.