Slow opening of excel docs via network share

 
Just setup a new client of mine with a sbs 2008 server. Server is running 12 GB ram & has raid 1 for os & raid 5 consisting of 3 146 10k sas drives for the data.
 
The end users are suffering extreme slow down on their workstations when they to an open an excel document from the data drive. It can take up to a minute to either open or save a document.
 
I think i have narrowed it down to the on access scanner (savservice.exe) on both the server & workstation as when i disable this option the slowdown is no longer current.
 
I do realise this is a security risk but i would have thought the server specification would easily be able to handle what the client is throwing at it without any issues.