EDIT: After working for a day, it got back to 75s before loading. Ignore this "solution", it will not solve the browser issue, although it may be good for your performance in general.

Check to see if you have a DLL folder inside the Arma3 main folder. This folder is used to retain some alternative memory allocators.
Thing is that running Windows 7 or newer doesn't require these memory allocators, in fact, they are less efficient than Windows 7/8, so I just got rid of the folder and everything was back to normal, now it takes 2 seconds to load the browser.
Running Windows 8.1 x64 here.
If in doubt, just rename the folder (instead of deleting it) and try again.
Cheers.