Only 3 of my many purchases in cydia show up on my jailbroken ipad 2.
They all still show up on my iphone 4. The same cydia account number shows on both.
Is this a known problem or is it just me?
It sounds like you probably have multiple logins associated with the iPhone 4, but only one login associated with the iPad 2. Try logging in with your other Google/Facebook accounts and seeing if the purchase records fill out.