Exactly the same problem.

45FPS single player on High settings, 5 - 10 FPS on multiplayer on Low settings.

Q9450
GTX 460
8 GB Ram
Windows 7 64 Bit

Same here, it is still playable on multiplayer, but gets annoying
i5 3,4 GHz
GTX 560 Ti
8GB DDR3
Win7 64bit

Same here getting around 40-72fps (my monitor runs at 72Hz)
When I join ANY MP server it drops to 15-30 fps

i7 3770k OC'd 4.2Ghz
SLI X2 GTX 570 OC'd at 800Mhz
16GB G.Skill Sniper
Win7 64bit

Exact same here. Fine FPS when in single player and join a MP server it goes down to 25-10

FX-8350
GTX 660ti OC'd to 1095Mhz
10GB of stock ram that came with the system 665Mhz (lol)
Windows 7 64bit

But.... I think it might have to do with the internet connect I only have 6mbs/1mbs (down/up)

same here theres simler posts on here hope the devs listen this time cos arma 2 had the same problem and they ignored it :(

Absolutely The same thing for me, I Can run the game on Ultra settings in single player,and get between 40 to 60 fps but as soon as I try playing in multiplayer... Doesn't matter if I set everything to low and turn off everything that I can I still get between 10-to 15 fps

AMD Quad Core 9950 2.61ghz
16gigs of Memory
3gig GTX 580

same here. I think it has something to do with the CPU having to deal with all the AI bots...then again maybe its a larger problem.

P.S. - I think if they can fix this(along with the game breaking hackers), they will have a title that will easily compete with COD and BF.

the problem is the game is not utilizing CPU or GPU power aslo setting graphics settings to low forces them to be computed on the CPU not the GPU so can actually make your framerate worse

Duplicate of #1264

Indeed.