rootkit?

avast fround this 2
one is MBAM and other is from rogue killer I d/l
do I delete or they false?

Your assessment is correct, they are false positives

any idea why they popped up now
have had MBAM for ages and not had this b4
also rouge killer didnt flag up last time i did it
do i delete?

Both MBAM and RK are regularly updated. Avast looks at the behaviour of files to determine if the are exhibiting rootkit like behaviour
There should be an ignore option in the dropdown