Excel 2010 very slow to open and close files over a network

Hi,

We have just moved from XP and Office 2003 to Win7 and Office 2010.

Since the move 15mb excel documents across a 2mb network are really slow to open - like 5 mins.

It was 5xfaster with XP and Office 2003 and the servers on which the info resides are 2003server (i've read the hotfix affecting 2008r2).

I've tried a few things that I've come across on google (registry tweeks and disabling something in IE but it's no better).

Any ideas gratefully recieved.

Thanks