I can't help with this particular error, but I can say that I self and a bunch of my co-workers have exactly the same install (Ubuntu 10.10, 64 bits, Helios (3.6.1) and JBoss Tools 3.2 beta 1.
On our systems installing works, so it's perhaps not really the platform combination.
I am able to resolve the problem. From the Jboss Tools 3.2 Milestone used only following tools:
Jboss Web ...
Till now i did'nt found the reason for the problem. However, my needs are satisfied.