If you link to a bad neighbour it will affect your rankings. Ensure you don't link to any dodgy or spammy sites.

I think removal of outbound link will not affect you ranking not unless it's inbound link.

It depends on the page rank of your inbound links and how many external links you have and what the quality of those links are.

Are you talking about changes to the sites that you link to that are beyond your control? If you think that a site might potentially change to include something you wouldn't want to link to, don't link to it. Period.

I had a PR2 on my links page.. Then went and redid it and removed a few links that didn't keep mine up and so on... Next thing my PR was gone... I have no idea what is going on, however I did loose a few other PR's on other pages too. (maybe because I redid them too!)

I think to take off outbound link from your site should not effect your PR.
But if other take off your link from their website (inbound link) that will definitely effect.
Other is about the content of your page, if it's the real unique, no one copy you (which you may not know, use copyscape to check it) then it should be ok for page rank. Oh, one more. Make sure that you didn't link to any dodgy or spammy sites as seogoat said.

generally speaking no. but when you remove an outbound link to a high quality site it does make a difference - because your page is getting "credit" when it links to good page.

^^ do you mean to say that its good to link to good ranking sites??

Yes outbound links do NOT affect the PR of a page, they will dilute the amount of PR a page can transfer to another.