All information provided here are just for the troubleshooting purpose, any failure or dataloss occuring by following the steps below is not my responsibility, use at your own risk
Hi... friends..
here is the solution to your problem, the problem is caused by the driver for GT525M by Dell which is a driver from nvidia only but is customised for dell laptop.. (OEM version)
you can go to nvidia support site and download the latest driver release the link is here
http://www.nvidia.com/Download/index.aspx?lang=en-uschoose your graphics card and OS version then click on search
the latest driver release is 285.62 WHQL(windows hardware quality labs)
download it and perform a clean installation..
this driver update will also solve one of the problems of GT525M on Dell due to which
Mudbox 2012 both 32-bit or 64-bit do not start(process executes and uses all resources but UI don't load)
after installation of this driver from nvidia official site everything should work fine
(but make sure you do a clean install- clean install means uninstalling previous driver, restarting pc then installing new driver and again restarting pc)
i tested and confirmed the Mudbox problem's solution on Dell Inspiron 15R N5110 with NVIDIA GT525M myself
hope this helps for the viewport slow problem also...
Good luck