Shared Files Visible But Can't Copy?

I have a couple of desktops and laptops connected on a wired network. I have no problems accessing and copying files. This isn't about access denied or other machines not being visible. My issue is that one of my laptops can be accessed and I can move through all shared folders but sometimes when I try to copy a file from this machine the copy dialog opens but no data is being copied. The transfer rate stays at 0kb/s. Rebooting this machine helps partially, but file transfers will start at well below 1Mb/s and very slowly rise some during the copy. I don't have this issue with any other machine. In fact, I have never seen an issue like this. Most people have problems with read/write permissions, again, that's not my problem. Data just won't move when copying sometimes. All machines are running Windows 7 ultimate and avast 5. The laptop with this issue is a Toshiba e205, core i5, 4gigs ram, atheros ar8152 ethernet. Should also mention that I don't have a problem with other traffic on this connection such as internet or like I said accessing shared files in explorer. They just won't copy.