For some reason the latest patch has had issues with nvidia mobile graphics cards. I wont go into detail with the specifics (it regards a renamed .exe), but I dropped from about 40fps in the mechlab to about 10 - 14. This is how to work around that issue.
First open your NVIDIA control panel, which can be found in your normal control panel settings.
Secondly, click on the manage 3D settings tab on the left, and click the 'add' button.
This will open a pop-up window. Scroll through and find the mwoclient.exe in your install folder. Default location is: C:\Games\Piranha Games\MechWarrior Online\Bin32\MWOclient.exe
From there, change your preferred graphics processor from intergrated (which is the core of the issue) to your nvidia high performance card, then click save on the bottom right corner.
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That should return your fps back to normal. Note that this fix only concerns mobile nvidia cards, but im told the theory is similiar to mobile AMD chips.
Edited by Alymbic, 29 October 2012 - 05:33 PM.