Problem streaming from NAS to Windows 7 PC

I had been using my ReadyNAS Duo Mk1 NAS with my Windows 7 32 bit PC (running an i5-2500k with 8g memory) for a while with no problems.

It streams to my WDTV Live Media Player over ethernet & works perfectly with no problems at all even with 19g 1080p files.

I decided to change to Windows 7 Prof 64 bit and did a clean install.

It all works fine except when I try to stream from the Duo to the PC by double clicking on a movie, again over ethernet (just to check on files) is stutters on the larger files, in places with plenty of action, which it used to play fine before in the 32 bit version.

If i copy the file to the PC it plays perfectly.

It copys from the Duo to the PC at around 200Mbps, and when it's streaming to the PC at around 10 Mbps.

I have tried Media Player Classic Home Cinema & VLC which both have the same stutter when steaming, anyone have any ideas where the problen could be.

Anyone have any thoughts on this please.

I have the problem even when playing a 65 meg mpeg

You might need to install 64bit codecs to allow it to run smother. I use k-lite Download K-Lite Codec Pack

They state that you should install both a 32 bit version and then the 64 bit version so i always do the mega and then the 64 bit.

You also might have something running on your PC that is hogging up your bandwidth. Do you know if your NIC is a 10/100 or a 10/100/1000?

To check if something is hogging up bandwidth.

Type resource monitor press enter.
On the top you will see tabs. overview, cpu, memory, disk, network. Select Network.
Let it run for a minutes then post a screen shot of Processes with network activity and TCP connections