Sorry, EntityManager is the class I am trying to inject.
What is the problem you're specifically having?
http://unrealities.com/seamgwt has an example of calling a Seam component with an injected EntityManager, so I know it's possible.
Unfortunately, that example uses Seam 1.2, and there are some problems getting it to work with Seam 2 (which I've blogged about here: http://blog.robjsoftware.org/2007/11/gwtjsf-broken-with-seam-2-sorry-folks.html )
Anyway, I hope to make the time to fix this all up by the end of the year or so.