I've seen some of those interactive flash banner ads consume 70%+ of my 3.06GHz CPU. So you may not actually be locked up; it's probably just hogging 100% of your older CPU. Granted, most websites using flash don't cause a problem, but when TVTime with greedy deinterlacer only uses 20% and a DVD movie only about 5%, I really can't imagine how craptacular macromedia's code must be to waste 70%.
My solution: don't install flash or if it's already installed disable it. When they straighten out the spaghetti code that somehow passes as a usable product, I'll give it another try.