Installing RAC does always have some nice surprises.
For example the following:
Although CRS and cluvrfy did not pose big problems (from what I've heard - didn't do it myself) the node could not be found.
SSH works - of course.
After some trying the decision was made to open RSH on both nodes.
Voila. It works.
This was on an AIX 5.3 . So this might be of some help for you out there.