Hey mate,
1) Did you try to update your drivers (especially graphics card driver. You can find it on SRO homepage in downloads section.)?
2) Does this happen only when you play (try to play

) SRO or it happens in other games also, especially online ones.
3) Did u try to minimize SRO by hitting Windows key > clicking on "Show desktop" shortcut icon on your toolbar > swith back to SRO again.
My sister's comp is like that and #3 works well on her computer. (a laptop which sucks lol)
Well .. That's all i can think after a sleepless night playing SRO all night long.
May be others give you better solutions.
Take care