Ear training is something almost anyone can do, but it's easier for some than others.

This sounds obvious, but the key to developing your ear is to listen...(bare with me here, the advice will get better, I swear!) You're trying to pick out a particular instrument or voice in a "wall of sound". One of the easiest one's to find is a vocal harmony. Earphones can really help you as a lot of songs have the melody and harmony panned to different speakers, (assuming you can listen in stereo!) Once you've developed the ability, you can apply to any and all instruments, (guitars, bass, drums, mandolins, violins, cellos, trumpets, harmonicas...I'll stop there before I get carried away...)

Listen to 'Space Oddity' by David Bowie with both ear phones in, then listen with just the left, followed by just the right seperately. Once you know how each side goes, see if you can pick out one or the other when you listen to it normally. When you're learning, it's useful to actually know what you're trying to listen for!

As for strumming patterns, do you mean you have problems actually playing them, or just hearing what the rhythm is when you listen to a song?

Hope that's of some use!