Since updating itunes to 10.1.x downloads went from minutes to many hours

Question

I have a business class internet service which provides 25 mbps down and over 10 mbps up.
Before updating to itunes 10.4.x, an HD tv episode would download in a few minutes, always less than 10 minutes.
Since updating
1) itunes became unstable and crashed regularly
2) it refused to play ANY HD video.
3) downloads from the istore went from a few minutes per episode to many hours
I did all the normal fixes
itunes repair
itunes deinstall and reinstall
itunes and quicktime deinstall and reinstall
rebuilt itunes library
rebooted numerous times
rebooted cable modem
checked speed and verified minimum speed out of several tests was 12mbps
observed download performance in itunes where download started at 2-3 mpbs but rapidly dropped off to 50 - 100 kbps
monitored network performance and observed that most of the time the itunes client is waiting for inputs from itunes store server.
Generated a trouble ticket and have been through 3 levels of "go try this" with no improvement.  At the stage where maybe I might get access to an actual support tech.
I am coming to the conclusion that this is a problem at the source where the server servicing the download is either very busy or slow which is creating a long wait period between packets.  Basically my itunes client is sitting and waiting on the store for 9 hours to perform what used to be a 15 minute download.
Is anyone else seeing this problem?  Does anyone have a recommended fix? 

Answer 1

Thank you for your reply. I resolved with advice from 4 year old post instructing "holding down option key while restsrting iTunes and choose the preferred library", but  thank you again,