Here is an interesting question I'd like to pose for you.

Name one animal that habitually drinks the milk of another animal after it is weaned from its mother?

Yes I can see that , but the excavations in Azerbajan and other stine age archaeology do report tethering posts. I would think that the lactose problem may not necessarily be due to what we think but could be more to do with genetics, plague killing off people etc and movements of peoples, as many people do not have the intolerance.

Also as to the general milk thing..we eat EVERYTHING we can put are hands on animal, vegetable etc and getting some free milk from a pregnant animal would be logical.

Some tribes may have done this others not depending on where they are and the avaiablity of animals and types of animal.

Hunter gathers eat tnnes of differnt things, some creep, crawl and we wouldnt eat them nowadays LOL !...

ancient people must have been intelligent just different, no metals etc but they were clever in fint and wood and hand weaving etc, I study wildcrafting and bushcrafting and you realsie through doing it that theres so much the ancient people could do !

This probably enabled humans to drink more milk from their mothers for longer time - I really have no idea why the mutation came along and spread - could have been completely random, or maybe some humans did indeed begin to drink milk from other animals.

There's actually pretty strong evidence that adult lactose tolerance spread because of bovine milk in the diet.  For example, cattle were domesticated in northeast Africa about 9000 years ago, and the mutation that originated there for adult lactose tolerance started becoming common about 7000 years ago:

http://www.newsdesk.umd.edu/scitech/release.cfm?ArticleID=1376

This was after the paleolithic, in the early neolithic period, and it's likely that the alternative to drinking milk for these populations was starving.  In the same time period, agriculture was spreading, human populations were booming, and people were becoming smaller and less healthy, etc.

The north European mutation for adult lactose tolerance is a different mutation with the same effect, and originates in another area where cattle are thought to have been domesticated early.

The fact that multiple mutations happened so recently with this effect has an interesting reason.  They are all in the same region of chromosome 2.  This region of chromosome 2 is a small distance upstream of the genes coding for lactose digestion, and is likely responsible for turning lactose tolerance off after infancy, so any mutation that damages this region allows the gene for lactose tolerance to stay on into adulthood.

As you say, that doesn't mean we're suited for utilizing all the other ingredients in cow's milk effectively.  That would likely require the development of entirely new genes, not just a point mutation to turn one gene off, and entirely new genes made up of many base pairs would take a lot longer than 10,000 years to develop.