If this is a one time thing, then it may need some patience. I've waited up to 40 minutes before on a guide download before on a 722. Of course, there were several start-overs and manual receiver re-boots and manual check switches along the way to add that 40 minutes together.
I find with my experience that it varies throughout the day how fast the guide downloads. I don't know what the variables are that affect it. Lately it's been about 5 minutes but usually takes no more than 10 minutes.
If this is happening every day where the guide does not download properly and you've checked to ensure the automatic nightly updates are enabled on your receiver, then you may very well have an a technical issue that requires a phone call to tech support and more possibly a tech having to roll out.