I had a system here that I was running on wireless. It would communicate fine on a fresh boot but after a while the wireless would just ... stop. No reason I could find. A reboot always got it going again. I put it down to the wireless NIC going to sleep and not waking up on network traffic, but it wouldn't wake on local input either. I just threw that card in the bin. This was on Win XP, btw.
I'd guess (but that's all it is) that your wireless NIC is to blame and it wouldn't matter what OS you were using it'd do the same thing.