OK (sorry to be avalanching in this product thread Deceptor and others

ops: ) but I need to clarify something further:
I have the vBOptimise product on and passing all tests on my smaller board - it does not throw the wierd 'maxloggedin' error on editing and saving posts. This is therefore a "full" implementation of this product and the vB core memcached datastore engine...
Further I have commented out the "$config['Datastore']['class'] = 'vB_Datastore_Memcached';" line - and only that line in the bigger board config.php and can say that the vBOptimise system tests are all passing - so this is encouraging - especially as I can still edit and save posts there ...
BUT and this is a big BUT... Despite having separate "prefixes" for the two sites they seem to be merging a lot of the common (but different) cached data - ie my forum logo, all the ads served up by openx - various image elements from the css's.
I have had to switch to filecache on the smaller board to stop it inherriting all the stuff from the bigger one.
I doubt that I have the expertise to sort this out right now and it is very hard to full explain - I also don't want to spam the thread of your excellent product.
So I will await any suggestions otherwise I'll sit tight and see what my users say - if its somewhat better I'll leave it at that for now!
Thanks again and sorry for the verbose troubleshooting posts!
Will