I've been having a similar problem with Dexpot 1.4.2 build 768 and Maxthon 2.5.2.6608-beta4.

Dexpot seems to get confused because by default I have Maxthon setup to 'Always show the system tray icon' and 'Minimize to system tray'. When I clear both these options Dexpot works properly.

Update:
Removed VMWare version 2 from system (replaced with Sun Systems VBox) and rebooted, Dexpot now seems to be behaving OK.

Rod.

Dexpot 1.4 has been running successfully since september 2008 but has suddenly broken.

When switching desktop, background is not cleared so previous desktop is still visible. New desktop Windows and Icons appear and work correctly but new background is not painted. Dragging windows with in desktop now leaves portion of moved window in old position - again background is not being cleared.
Disabling Customized Background doesn't help.
With customized background enabled, image does change (as seen though trransparent areas in DeskTop Manager and when windows are moved) but background is not re-displayed on switch.

Have been running 1.4.2 build r757, just tried build r768 and 532 - still broken.

I have made many changes to system recently, including new motherboard and new applications, but none coincided with the apperance of this problem.

System is Windows XP Pro, sp3, Version 5.1.2600.5755

Hardware is:
Intel DG451D mother board, 6GB ram,
Intel Core(TM)2 Quad CPU Q8200 @ 2.33GHz
NVIDIA GeForce 9300 GS, dual monitor