Our PR value suddenly dropped after we moved away from our previous SEO company. It occured within a day or two, should I attribute that to their efforts or should I attribute that to any changes we made after we moved our SEO efforts in-house. I would think it takes weeks/months for PR values to change.
I would advice you to go thru this... it helped me a lot... I dont have any SEO company hired... All the stuff I do it myself http://www.smashingmagazine.com/2007/06/05/google-pagerank-what-do-we-really-know-about-it/
I am surprised at the speed with which you lost PR! Even if the earlier SEO company removed all their generated back links, it is very unusual to see a drop in just 2 days! I guess.. it would be just a coincidence and the fall can be attributed to your backlink source sites getting penalized! Regards, RightMan