1 the user entering the keyword and reading your add doesnt like the contents or he is not looking for something ur going to offer.
as a result he doent click ur ads and ctr goes low
CTR of 1.2 should not disable ur ad for particluar k/w may be ur competitors are having higher ctr for the same
2 you can try to change the contents of the ad and try choosing different keywords combinations
For the ur competetiors ads you can ur self search google for same keyword and see whats coming up and why
With Regards
1. Are you using all the matching options?
[webmasterworld.com...]
2. Are you using negative keywords?
[webmasterworld.com...]
3. Are you trying out multiple ad copies?
Sorry, not at computer with all my bookmarks.