I run been working with Mcafee since 1998, and I have seen this many times. What happens is, when the machine tries to update the virus definition files (either by FTP or copying from a local computer), the update gets mangled.
There are 4 DAT files that get updated every time your systems reach out for the latest update, SCAN, NAMES, CLEAN and INTERNET (INTERNET is optional). So, when these 4 files are extracted from the Update DAT file and imported into the local installation of Mcafee, sometimes it just doesn't work right.
When these DAT files are not all updated at the same time, then you get this problem. Mcafee will not start, no matter what you do. You right-click and choose Enable; nope. Reboot; no such luck. Try and run the DATupdate again; no way.
Here is what you have to do: set the 3 Mcafee services to a Manual startup, then reboot.
When the machine comes up, and you are asked if you want to start Mcafee, say no.
Then, get the latest DAT file (from ftp://ftp.nai.com) from NAI, and extract the 4 DAT files. The update file is a ZIP, so just use WinZip to extract the files.
Then put the 4 files in \Program Files\Network Associates\Netshield or ViruScan folder.
Restart Mcafee services.
The thing I have noticed also is that, once a machine starts having problems updating the DAT files, it will ALWAYS have problems, until you reinstall Mcafee. So, keep an eye on this machine.
Hope this helps.
