Pclos now working very well.

Got various replies to my post in the pclos forum. One of these said that you MUST update the system immediately after installing.
This did the trick very nicely and everything worked very well after this. No problems.
Actually, I feel a little silly that I didn't pick this up myself. The very first line of the pclos quick-start guide says the very same thing.
No excuses here -- bad slip-up.