Home Sharing issues - can see each other's libraries, but can't transfer

This is between my 13" MacBook Pro and my Dell Inspiron 530 desktop. I do most of my music listening on the desktop, since it's hooked up to my nicer speakers. I want to transfer some of the music over to my MBP, but it's not working - I transfer one or two songs, then it comes up with a "There was a problem downloading "songname". The network connection timed out."

However, when I try to transfer songs from my MBP to my Dell, it works flawlessly.

The thing that has me confused is that it used to work both ways great. As far as I remember, I didn't change a single setting - there shouldn't be anything different between the computers, and yet this inexplicable error is coming up.

Any ideas?! I'm tearing my hair out here! My iPod touch is set to sync with my MBP, so I don't have any of my recent music on there, and it's driving me crazy.

Also - before anyone suggests this - I already disabled AVG and the firewall on my PC/desktop, and I also disabled the firewall on my MBP.