A PR issue

Hii...

I recently (2 months back to be exact) changed my domain name from site1.com to site2.com. ALL old URL's 301 redirect to new location. Everything's FINE till here!

site1.com still has PR3 whereas site2.com is still PR0. WHY? I have read at so many places that doing a nice 301 redirect of all old URL's to new location would also carry forward the PR.

On 28th May when PR updated, my site2.com showed PR3 BUT just for 2 days. After 2 days, it again went down to PR0. WHY and HOW did this happen??

By the way, I seriously do not care about PR much. The only reason this is troubling me is because of advertisers. I made over 100$ in those 2 days when PR went up, but suddenly it went down on the 3rd day i.e. 31st May which definitely affected my revenue as advertisers care a lot about PR.

I need your views on how and why did this happen.

Thanks

You can see changes if you hit different data centers.

What does Google Webmaster Tools report for your external links to site2?

It reports the same as site1 i.e. approx 1500, clearly means that 301 redirect is working as it should.

Your traffic is fine? You may have to wait for another update to see it return.