Small Engines (Lawn Mowers, etc.): Echo weed eater, straight shaft, oil mixture

Question
Used my straight-shaft Echo weed trimmer for the first time this summer.  Cranked right up and ran well for about 45 minutes. I then shut it off for about 10 minutes.  When I tried to crank it back up, the cord didn't pull. Removed the cord apparatus and found that the whole shaft was frozen.  Any ideas as to what happened? By the way, I did run it with the old gas/oil mixture in it. Could that have caused a problem?

Answer
First thing to do is to pull the muffler and look at the piston,
it is likely damaged, pull the spark plug and try to see if it will
budge, if you see damage, the repair will be high, piston with rings alone will be over $90.

Could have been caused by a partially clogged carb, or by running old gas.