If you didn't have any problems with prior strumming patterns, then this one won't give much difficulty either. This is another common strum, which is just a slight variation of several strums covered earlier.
Let's take a moment to listen to what this strumming pattern sounds like at a slow tempo (MP3 format). Try and internalize the rhythm of this strum before you even attempt to play it on guitar. Say "down up down up up down" along with the audio clip. Once you feel comfortable that you know the rhythm properly, pick up your guitar, hold down a G major chord, and try strumming along.
If you can't seem to get it right, spend more time practicing the rhythm away from your guitar. I can't stress this enough - the key to learning strumming patterns is to be able to "hear" the pattern in your head before you try and play it. Once you've gotten the hang of it, you'll want to try playing the same pattern at a faster tempo (MP3 format).

Remember:

• If you are playing an acoustic guitar, make sure to strum directly over the sound hole
• On electric guitar, strum over the body (different locations will give you different sounds), not over the neck
• Make sure all strings are ringing clearly
• Make sure the volume of your downstrums and upstrums are equal
• Be careful not to strum too hard, as this often causes strings to rattle, and produces an undesirable sound
• Be careful not to strum too softly, as this will produce a "wimpy" sound. Your pick should be striking the strings with a relatively firm, even stroke
• Think of your elbow as being the top of a pendulum; your arm should swing up and down from it in a steady motion, never pausing at any time.
• Having said that, the bulk of the picking motion should come from a rotation of the wrist, rather than from the forearm. Be sure not to keep your wrist stiff when playing.

Let's use these new chords and strumming patterns by learning some new songs.