Windows 7 - Media Centre / WMP very slow displaying wpl playlist

I have for some while been having an issue with my Windows 7 MCE (Home Premium 32 bit) playing a playlist created within MCE. All my music is store on a NAS drive. Playing an album is no problem, but if I create and save a playlist it takes 3-4 min to display the playlist !
I had little time to investigate until recently when I decided to upgrade the hardware of my MCE. After doing so with a completely clean install and hardware I find it does exactly the same taking 3-4 min to display the playlist, effectivily locking up the machine until it deplays.
My subsequent investigations have shown the following :
I also have another machine on the network running Win 7 64 bit, if I run MCE on this machine and link it to the same music folder any playlist run within a second or so, quite acceptable.
Whilst trying a few things I discovered that MCE and Media Player by default save as wpl but if I saved the same playlist as an M3U in Media Player then went into MCE on the 32 bit machines then they played straight away.
Whilst this gives a work around I wondered if anyone else has come across this problem and knows what it could be.... have I configured something incorrectly ?
Opening both files up in note pad the showed the same path details to the mp3 files.
I would appreciate anyone elses views.

Thanks Derek