Toshiba 3TB Ext HD not recognized

Hi I am running win7 Ultimate 64bt and had my Toshiba external HD for nearly a year. All of a sudden after my latest windows update it wont recognize it. It says : "USB not recognised".
It comes up in my device manager under USB controllers with a yellow triangle but each time i have tried to update the drivers it says they are up to date.

I have bought several bits of software to fix the problem to no avail. Toshiba are not interested and I have received no reply's to my queries and really am getting worried. I have many years worth of data on the external that is irreplaceable and thought buying an external drive would solve my problems if my system ever crashed, obviously i was mistaken.

I have read several forum blogs and this seems a common problem, but the answer still evades me.

Please please can someone help me. I am distraught that I have lost all my data that i have been collating over a long time.