You sound like in the same boat as me...I have that same similiar problems but I tried a regstery fix and it seems to have controlled the lockup or freeze problem so far here is the registery fix I used but before you do so make sure you backup your registery before doing this fix. But if it don't work just delete it as it is a addin registery not a registery that will be modified.
Try this and see if it work. The dword value is put in a decimal 16384.
This might or might not help but I have XP pro SP3 and it seems to have not gone network system 100% locking me out. But I keep using this regedit and see what happens. But so far my system is stable.