I have iPad2 and downloaded a free version of Remote Desktop Lite - RDPBy MochaSoft.
It connects to my Terminal server 2008 ONLY IF the user account has administrative previliage.
When I read FAQ from the software company website, it says it would not support Terminal Server connections due to a licencing issue with Microsoft.
However it make the connection as long as I use administrative account. I can make this user account as part of administrative group, but I prefer not to do that.