What dashboard are you using for the transfers?
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this article. The error you're getting is a Winsock error, and you're the first person to report this problem. I've never seen or heard of an error 10055 even when working on xFER.
If you're not using Avalaunch with Boost, I'd try it first. It'll be faster for you, and it shouldn't encounter this error unless there's something really weird going on with your box. There's also a setting in the Avalaunch XML that could help you tweak the port range used.
If you're still not going to use Avalaunch (which is the only way I could even imagine this error happening) then I could suggest turning on passive mode, which forces the the dashboard to become the server, so the port problem shouldn't occur. I know, it sounds weird, but normally with FTP, an FTP client becomes the server, but like all good things that came from the UNIX world, they did it backwards. Passive mode reverses this and tells the FTP server to actually be the server.
If you use EvoX don't bother with passive mode because it doesn't support.