using PS5 I got "inkblots" while working on details

When I', working on details in PS5 I often got big blot's like if you use a defect pen.

I'm using a notebook with CPU i7-2640M, Nvidia GeForce GT 525M and for Input I'm using a drawing board Wacom Intuos 5.

to fix this problem I've updated Graphic driver, reinstalled CS5, reinstalled Win 7 and CS5,

but nothing could fix this problem.

I have an older Notebook (it is very slow) with my drawing board, and on this hardware everything is ok.

But I need to get a solution for my actual notebook.

Thanks in advance

Marnie