When Downloading via FTP, my PC will not let me surf the web

[UkrainianThor]

Hello gentlemen. About 2 weeks ago something very strange happened. When I was downloading stuff from my seedbox via SSH FTP, I was no longer able to browse the web. All the sites were constantly timing out.
I've never had this type of problem before, I always multitask, I do my other work while I download, and I haven't changed anything that I am aware of. I still use Filezilla, and Firefox & Chrome. Has anyone else encountered this problem before?
I run Windows 7 Home Premium, but I don't think that should matter. I would appreciate your help.

[smcewa11]

New version? Try reverting to one a couple before 3.9.0.3.

Usually this happens when you max out the upload and there is no upload left for ack's. Try setting the program max download speed to a bit less than your actual max download speed.