Performance Issue [Battlefield especially]

hi guys
I have an m14x r2 with th 650 2gb 8gb of ram and the i7 3610qm
I bought the pc and I could play every game (including battlefield 3) maxed out
after almost 4 months I get some really weird fps drops while playing battlefield... i go from 45-50fps to 12-15 fps in a matter of seconds
this happens after I changed the settings from ultra to low (really low...)
please help me
thanks :)

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ah... this happens only when I play multiplayer... in single player no problem with the fps
 
Only in multiplayer
I already rest my router etc etc but the probpem persists
I disassembled the pc t clean it fron the huge amount of dust inside of it
I will try again

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PROBLEM SOLVED!
I just had to disassemble my pc and clean it from the dust (there was loads of it)
now I get almost 45-50 fps with all details on ultra
I also did an OC to the GPU with afterburner (+120,+60) and to the CPU from the bios (+50,+51,+90)
Now its awesome to play on the M14X
Temps also decreased.. now with GPU and CPU at full load I get a max of 61° for the CPU and 64C° for the GPU
thanks for everything :)

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I will buy also a cooling pad and the diamond thermal paste to decrease even more the temps
Furthermore, I will bring the ram from 8gb to 16gb :) (I just need money... xD)