I've never had a clogged dip tube from gelatin,either. OP -what was your procedure, out of curiosity? Even if the gelatin mixture were overheated to the point that it literally turned into a layer of jello, I'd think that enough gas pressure would push it out.
Is this an IPA by chance? If so (depending on your hopping procedures) your dip tube or poppet valve could be clogged with hop debris, which happens to some brewers.
Regardless, for the future, this gelatin procedure is the most foolproof I know of. Used it many, many times with success:
http://www.bertusbrewery.com/2012/06/how-to-clear-your-beer-with-gelatin.htmlEdit - I agree with the advice to turn the pressure up a bit higher, to see if the clog will clear. Worst case, you could vent the keg pressure and pull the liquid poppet, then the dip tube, and inspect to find the clog. Good luck!