One of my clients page rank has dropped from pr 3-2 and i can't find any reason why. Could anyone tell me if the new algorythms have caused this issue with other sites.

You should use seo off page technique with quality and quantity also remember comman mistake before submit your sites, so try again in a manner i think result will be better after somedays...

Link buying/ selling can be one. Here is Matt Cutts helping you with many more possible reasons for a PR drop:
http://www.youtube.com/watch?v=kFcJ7PaLoMw

Try to build some dofollow quality backlinks.
They can help to get high rank.

Determine how many of your old links are still indexed and determine where to go from there.
you need a benchmark and PR is a basic data point to model.

If you are working with off page activities and still it not works to get the back links then my suggestion is that go for the Link wheel strategy because it will give you lots of hope to get the back links to your site and once you getting the back links then your page rank will be automatically increased.

And sometimes it's just crap-hat tactics like these that will inevitably lower your websites credibility with Google.