Help with Ringtones

[Da Uniq 1]

My GF's ringtones sometimes work and sometimes dont.

Not new to Android but new to this phone, Samsung Nexus S 4G.

Set up notifications folder like previous Android devices.

She is missing calls a lot because her phone doesn't ring all the time.

Only fix I have found and is a temporary fix, Slide the bar on screen to silence phone, then slide it again to turn volume back up?

Any one else experience this or know how to fix?

Non rooted - and stock