iTunes 10.5 Video choppy, stuttering.

Just before I updated to 10.5 (64bit) all my videos including the HD versions all played smoothly and fine, now only the SD videos are playing ok.

If I play them independently in Quicktime they are lovely and smooth as they should be, also in other apps such as PowerDVD and VLC.

I backup my own DVD's for playing on the iPod Touch 4G and I use Freemake Video Convertor which has never given me a problem if I use the iPod Tocuh 4G settings with the higher quality resolution and it plays back choppy in iTunes but if I convert for the older iPod Tocuh 2G with lower resolution settings it plays fine, but I dont want lower resolutions when I know for a fact that the higher settings work, as they did before yesterdays update.

My puchases from App Store all play fine but none of those were HD. My drivers and codecs are all updated, I have uninstalled and reinstalled everything realted to Apple and my drivers and codecs, still no luck with iTines 10,5 playing my higher rate videos, frustrated.

Coinicentally Homeshare thankfully still streams them all smoothly to my iPod...small mercy's.