Paul,
If you searched for 1and1 in these forums, you probably already found that you're not alone. My experiences with 1and1 were so frustrating that I left them, as fast as I could! Their support sucks, and I never could get a DNN installation to work on their servers.
I urge you to run away from 1and1 asap! They will just give you an ulcer, all the while keeping you on hold, and collecting your money. If you're still covered by their "Satisfaction Guarantee", tell them so--by phone, email, and most importantly by certified letter. Cancellations require notice in writing.
I also tried Brinkster. They have problems with DNN, too. You'll find many forum threads regarding spontaneous logouts on Brinkster. No solutions put forth have solved that irritating problem. I'm convinced that the problem has to do with their server configuration. I cancelled my account there, again before my "Satisfaction guarantee" expired.
I've been with WebHost4Life (WH4L) for a year now. Their support is excellent, and they seem to be way more knowlegible with DNN, than 1and1 and Brinkster. They've quickly resolved any issues I've encountered, and happily answered any other questions I've thrown at them.
I say, don't beat yourself up trying to run DNN on 1and1. Cut & run!
Rick