Extended Desktop problem

[CaptainMintMan]

Hi folks,

I have:
Toshiba Sat Pro A200 laptop, 2Gb RAM, Celeron M CPU 520@1.6GHz. Screen is 1280 x 800 and is the RHS of the pair. LHS is a 17" 1280 x 1024 Goldstar VDU. They are setup as an extended desktop (to use the MS designation) and defaults to the Goldstar as the main VDU. I'm running Mint 17.1 with the MATE desktop.

The problem:
When powered up, the system correctly sets itself up, but does not allow me to fully move a window fully onto the laptop. I can move the window say 80% of the way such that it then appears spread across the two vdu's. It then refuses to go any further. Going into "Monitors" and disabling and "Applying" either of the screens, then re-enabling them gives full correct performance for ever.

Any ideas?

Regards,

CaptainMintMan