You could be nearish some fake ultrapeers you are connecting to.

Check these links: (a) Problems with the search, __ (b) Hostiles List

When you say lots of choices to download, are you sure they are not fake, at least a % of them? Check the topics here about corrupt or fake files, etc. -> MAJOR TOPICS for Upload/Download HELP

I'll move your post to the mac osx section. Stief might have some ideas.

BTW you may be having a problem with Out of Bounds searching (OOB). This can be disabled via your Speed settings.