I have the same GPU, but my problem is that the frame rates randomly drops to 10-15fps specially on warzones. It drops for like 3-5 seconds then resumes to its normal frame rates.
all low = 50fps
all high (w/o shadows) = 30 fps
Model: Acer Aspire 4755
CPU: i5-2430m @ 2.4 ghz
RAM: 8gigs
Vcard: gt540m with 2gig dedicated
driver: 301.24 (previously with 296.10, same problems...)