I'm getting the same issue, and on a desktop PC. What resolved it for you?
Also I would like to expand upon the description given above. (Although after just having used CPUID's HwMonitor, I think that my 88-112 degree (celsius) GPU temps are to blame for the lag)
The lag does indeed happen every few minutes, and all screens except for the 'esc' menu lag (Inventory, Crafting, Character options, Spells, etc). When I press esc, the mouse moves normally again, and the lag is not present until I exit the escape menu. The lag doesn't stop for at least 1-2 mins, and seems to stop sooner if I enter the escape menu.
Again, I'm thinking that this is due to high GPU core temps now, but I've seen a couple of other folks with this issue, and no details of what resolved it for them.
(for kicks, here's my (edited) DxDiag System Specs in a spoiler tag:
Spoiler
System Information
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OS: Vista? Home Premium Service Pack 2
HP-Pavilion NC692AA-ABA m9510f
BIOS Date: 09/10/09 10:25:18 Ver: 5.43
Intel? Core?2 Quad CPU Q8200 at 2.33GHz (4 CPUs), ~2.3GHz
8190MB RAM, Page File: 4012MB used, 12539MB available
DirectX 11
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Display Devices
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NVIDIA GeForce 9500 GT
DAC type: Integrated RAMDAC
Display Memory: 4069 MB, Dedicated: 997 MB, Shared: 3071 MB
Current Mode: 1920 x 1080 (32 bit) (60Hz)
Driver Version: 8.17.0012.8562 (English)
Driver Attributes: Final Retail
Driver Date/Size: 10/15/2011 00:53:00, 15693120 bytes
WHQL Logo'd: Yes
)