> I've recently moved to Chrome as my ISP
Chrome is not an ISP and, more to the point, the fact you've moved to Chrome has no bearing on throttling.
> no problems except that sometimes when I'm on AB I get an 'Internal server error 500" which means can't access a page
Again, this is nothing to do with Chrome, it's simply AB having a wobble which would still have happened if you'd stayed with your original browser.
> I go off AB come back on and its ok - but today - apparently my message is that My access had been THROTTLED'!
This one's nothing to do with Chrome *or* AB, it's that you're making too much use of your internet and your ISP (who ISN'T Chrome, remember) has decided to limit your access. Possibly you're downloading a lot of movies or songs ...