Thought id just throw this out here for anyone who cares for it.
Theres a backport for 1.9.1 if youd rather have that than 1.2.6, honestly i dont know if theres a big dif *shrugs*
but hey if you feel the need you can find it here:
Other Downloads - Mono
Just scroll down or ctrl+f "ubuntu" and youll see it there, its provided by badgerports.
adios