Originally Posted by brykins

What's happening when you try and download? Are you getting the "download unsuccessful" message?

If so, then there's a couple of things you can try, but in my experience (this has happened twice with my son's Pulse) they don't work and you end up with the last option:

Clear Market Cache
Force Close Market
Re-Boot

Remove SD Card
Force Close Market
Re-Boot
Re-install SD Card

Set Auto-Update of Time/Date to OFF
Force Close Market
Re-Boot

Set Auto-Update of Time/Date to ON
Force Close Market
Re-Boot

Last option: Factory Wipe/Reset the handset (this will lose everything on the phone - SD card will be safe, contacts and calendar are safe in sync'd to either Google or desktop)

As I said, we have had to do that twice with son's phone. One point there - when you factory reset phone, the FIRST time you go into the "My Downloads" section of the Market it'll list ALL your previously downloaded apps (free and paid for). Should you then exit the Market and go back in, you'll find it only lists the paid for apps. Good idea to write down your apps BEFORE resetting cos you're bound to forget something!