Hello,
I have same LAN hanging problem experienced on a Q2900 system, very annoying as I installed this 800kms away to look after my parents storage needs. I had the hanging problem initially when loading 3x4Tb of external disk data across LAN , probably 4 hangs in all. After the data transfer finished it seemed to run well for a month or so, but now any small copies I kick off seem to generate a fault again.
I also am using DSM 5.0-4493 , hopefully one of the other builds will fix this next time i have reason to visit the family up there, otherwise I will look at ripping the mobo out & installing something more robust.