Recently on two PC's Malawrebytes has detected "PuP.Optional.SweetlM.A"
potential malware, in a few registry entries. SAS did not detect them - neither did Avira anti virus. Maybe coincidentally my Avira anti virus was showing in Action Centre as not running and after a number of attempts I solved it by uninstalling and re installing. I have told MBAM to remove the threats. Google gives mixed views. Does anyone have a view as to how these get in - (I have W7, up to date, Avira a/v plus active web protection, Spywareblaster, MBAN, SAS, IE10)
"Curious that MBAB found it and the others did not"
That's probably because it's not strictly malware. As suggested by Woolwell earlier, you almost certainly picked up that nuisance when you installed a freebie and didn't look closely enough at what else was going to be installed (such as the "Sweetpacks Toolbar" etc).
"Malawrebytes has detected "PuP.Optional.SweetlM.A"
MBAM's classification is that it's a PUP (potentially unwanted program) and it's optional whether you want to remove it or not. You may also have noticed that MBAM didn't automatically select it for removal after the scan had completed.
So basically, you weren't really "infected" with anything malicious. Just keep an eye on what you install the next time you download a free program.