FPS/Ping Drop casting spell/skill

Hello!

In the last week I experienced an annoying issue: everytime i use a spell/skill my fps drop to 0 and sometime my ping go to 1k, I try to edit Video options but nothing change.

this is my pc spec

ATI Radeon HD 4800
1366x768
intel core duo CPU E450 @2.20 Ghz
2 GB ram

usually I play with 20 fps and 60 ping, I know my pc is pretty bad but I used to play with high details and no problem before last week.

Can the problem be linked with the resolution? I have changed monitor from a 1200x1000 to 1366x768 and before I didnt remember i had this problem.

additional information:
I have this problem with every class, in every map, solo or in party.
FPS drop every time some1 cast a spell: mobs, party mates, my character.

my problem can be linked with a more general FPS drop posted in this link:
www.pathofexile.com/forum/view-thread/126058

I noticed that FPS drop occur also when im exploring a new area