There are two companies licensed to produce generic lipitor for the first six months after the end of patent, which is about to end at the end of May. One is Ranbaxy which is making the product independantly and the other is Watson. Watson is actually selling the original Pfizer product. Now having said that, the active ingredient is identical in all products. The tablet must dissolve and give blood levels the same as the brand name. There can be differences in color, shape, and the binders and other inert products in the pill.
The FDA does post marketing data collection and if you believe that the medication you are taking is not behaving the same as the brand name then you may file a report with the FDA.
http://www.fda.gov/downloads/Safety/.../ucm082725.pdf
Keep in mind that just because one event follows another does not mean the first event caused the second (post hoc ergo propter hoc) The price for generic lipitor will drop amazingly in one more month. Look for the 3 month at 10 dollar kind of pricing as more manufacturers enter the marketplace.