There are not enough resources on the target computer to access files remotely.
Can be caused by low memory, insufficient resources assigned for network access, or anti-virus software.
IRPStackSize value needs to be increased in registry.
A reboot will sometimes clear up the problem, but a change to the network configuration may be necessary. (see below)
In registry (on target machine) go to HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\LanmanServer\Parameters. If the value IRPStackSize exists increase the decimal value to a range between 11 and 50. If the value does not exist create it (value type is DWord) and assign a value higher than 15 (which is default).