Systems Management

Hoping someone can shed some light on this one as I'm stumped!

I've set up a package and advertisement for CS4 Design Standard, at 4800MB content size. I keep getting the below error from the DataTransferService.log on the client;
GetDirectoryList_HTTP('http://**.**.com.au:80/SMS_DP_SMSPKGD$/STL001C6') failed with code 0x80070005.
Error getting network access account credentials. Code 0x80040215

I'm running SMS 2003 SP3.
I tested a "smaller" package and it deployed without incident. Access Accounts are identical on both packages.
My initial thoughts were that the package size is too large for IIS to allow access to...

The largest package I've successfully deployed for MS Visual Studio Pro, at 3500MB. Same DP.

Anyone have any ideas? I'ev been Googling this for the last few days to no avail!

Client cache is 6Gig

So I looked into the IIS side of things, modified the metabase.xml to changed

AspBufferingLimit to 5242880

Restarted the IIS services. Readvertise the package - still get the same error.
My only question regarding IIS is the amount of files (just over 310000 files) in the CS4 package could be causing me grief.

IIS6, Windows Server 2003 SP1

Thanks in advance,
Marc