Why are you checking in a DAT? Aren't you pulling from McAfee?
Start by looking at the EpoApSvr.log located in \DB\Logs folder
Contains details related to repository such as
Checking in deployment packages to the repository
Deleting deployment packages from the repository
Because it's not on a system connected to the internet!
I'll have a look at the logs files.
May I know the ePO server version and patch level? I will suggest you to upgrade to latest patch of the ePO server.
Make sure that you are checking in the correct package 'avvdatxxxdat.zip'.
If Application server service is crashing then I will suggest you to look into Event viewer for the message, it crashed with.
It's 4.5 Patch 4.