Please check what has gone wrong?

This google dance has caused a drop in my site's PR. The changes we made to the site are-
1. Added pages two months ago.
2. Added a very long list of business categories 10 days ago, which actually link to inside pages.
3. Did other SEO stuff like site map, external javascript, formatting through css etc.

In my opinion, it's the second change that has caused the trouble but I'm not very sure. I think so because the PR began to fluctuate exactly after that long list was added. May be it's some sort of PR drainage. Someone please tell me what has gone wrong. My site is www.indianyellowpages.com

One thing more- whhich of these hurts the homepage PR more- links to internal pages or links to other sites or sub-domains?

An advice is badly needed. Thanks in advance.

Maneesh I have you as a PR 5 so your not doing to badly, were you a PR 7 or 6 before? It may be just a case of lost backlinks. Has your # of backlinks increased or decreased?

Btw, the answer to your which hurts more questions is, it depends lol Sorry to be laughing but I just hate giving answers like that. Anyways more to the point, If you link to an external site and it links back great if it does not link back then you have not lost any actual PR however you have lost the opportunity to control the distributable PR internally, this being said, if you link to a page internally and that page link back to your homepage then thats great, however if this page does not redistribute either directly or indirectly to the homepage then in consideration of just the homepages PR that is just as bad.

Thanks for the relpy, seoguy!
My site was PR6 and the number of backlinks has <b>increased </b>by 27.
Like I said, the flux in PR was observed exactly after the addition of long list of links at the homepage. But all of them link back to homepage.
The backlinks have increased but may be that we have lost some high PR links or that the high PR of some links to our site has decreased. I'll check that out.

My site recently dropped PR from 5 to 4 even though my links increased so you're not alone although I'm afraid I've no idea why - perhaps it will go up again next month.

Nick