I am a new user of NBill and am still testing it out. I almost gave up on it before I got started due to the GoDaddy w/IonCube on PHP5 issue, that I see many others have been experiencing.
Fortunately, I found the fix during a google search and so that I do not take away from the original poster there (who I very much appreciate), here is the link http://www.marketingdao.com/helps/index.php?pg=kb.page&id=15
Also, during the install; I found that I had to change my php.ini timeout from 60 to 120
This 2 minute fix worked like a charm for me and I hope it helps others out as well.