Sorry for the delay in reply - got all caught up in Xmas & everything!
SO....want the good news?
I decided to put my hand a little deeper in my pocket & bought a Keyspan USB to Serial adapter for £30 from Expansys(.com) in the UK. I installed the driver that came with the adapter (CD) and plugged the thing in to a USB port on the Mac G4 (not in a hub).
I also bought a more traditional Serial (9 pin) to RJ11 lead from letsautomate.com (UK) who sell the lead alone for a few quid rather than buying the CM11 serial version in full. Connnected this setup to the new Keyspan adapter
Firing up Indigo & connecting to the CM11, I was given the choice of two ports (newly installed by the driver install process) & I selected "Keyspan 1" - no tech reason for this, I just tried it...50/50 shot eh?
Since doing this I have had no bricking of commands in the status bar & all the actions & combos I have set have worked perfectly & has done since last week in December. The only time lights haven't worked have been to my error in logic
The USB to RJ11 lead that came with the CM11 "USB version" is in the bin. The only thing I have had to do bizarrely is move my RF receiver as the remote was not working too well, but that's no problem
My simple advice to anyone suffering from the same issue - BUY A KEYSPAN!!! (in my opinion of course!)