This can happen in cases where the computer manages to have one or more security programs and if in new computers it could be a glitch which should be resolved automatically in a next update. Yet, could you please provide some more additional inforamtion on this like;
How old is the (Xp) computer ?
Please check whether there exists any other security software remnant in add/remove programs (or) in C:/program files & common files
Click about in security center and let me know the version of virus scan ?
To clarify, the XP machine was the previous one, with which I had no problems. It was about 3 years old.
The problem is in the new machine, about 30 days old, running W7.
The only other security program is Malawarbytes Anti Malaware, which I run on demand, i.e. not a background process.
Virus Scan is 13.15.113