To use Liam Lynch's words in his most recent viewer mail podcast (which can be found here:
clicky) "Writer's Block" doesnt really exist. This is a lovely and brave statement from someone as incredibly creative as him, but he also threw in a few cool suggestions for those moments where you need a jump start.
For one thing, trying a different artistic medium is always nice, regardless of your talent level in that other medium. For example, as Liam put it, if you're trying to write a book change gears and paint a picture.
Another thing he suggested was to take a magazine and randomly pick two pages with your eyes closed. Use those two images as the begining and end of a story and just fill in the middle. It seems simple and silly, and the outcome doenst need to be some kind of masterpeice, but it will definitely get your imagination going again.
Something I do for those kinds of moments is take a shower, sit down in the tub as it goes, and just meditate. I actually do this for all those tough moments in my life, but that's just me, all the white-noise from the water, as well as the warmth really let's me just forget everything for a while and start fresh. I suppose anyplace where you can find peace in this chaotic world would work too.
The most important thing, of course, is to not get discouraged!
Jam it back in, in the dark.