Can't access shares on system drive after installation of McAfee Security Center

I have a home network where a Windows XP Pro desktop system with 2 drives is
a shared server of folders to my Vista Ultimate notebook. Recently, my
Norton subscription was up and I switched to McAfee Security Suite , which
is free from my ISP - Comcast. Since then, I cannot access any shared
folders on my C drive (e.go. My Documents). I get an error stating "Not
enough server storage is available to process this command." I have 4
shares on my CO drive and all return the same error. However, Shares on the
D drive work fine. Login credentials for each are the same. Printer shares
still work fine.

I've seen postings regarding tweaking IRPStack Size and I bumped up that
value by 3 twice and then tried it at the max of 50. Problem remains.

Ideas appreciated.

TIA