[photon]

I'd blame something other than the software as well, it doesn't sound like software itself; when software uses a network resource it usually does so through Windows libraries rather than its own custom libraries.

Is there a difference in how the computer is connecting to the networked drive? I.e. connecting through windows network rather than a mapped drive? I've seen strange things like that before where if I access the thing through \\192.168.1.100 vs. a mapped drive they behave differently (though they shouldn't).

I'd also ask if the network resource is being shared in multiple ways (i.e. my NAS can share the same resource via NFS and Samba), maybe one is playing nicely and the other isn't and it's connecting a different way? Though it sounds like it's all Windows so that's probably not it.

You tested the network speed with copying a 500MB file but that doesn't really test the scenario you describe, it sounds like a latency issue rather than a transfer issue since the updates are small but there's 100 of them.

iTunes runs terribly if the files are on my NAS for this reason; transferring files is fine and fast, but the file access latency is higher and iTunes does a lot of individual file accesses for some reason.

Not sure if there's a tool that could test the latency of a network share.

EDIT: Could also try to update the network card drivers.