Homelite 26ss Trimmer Stalls Out after 30 min.

I have a Homelite MightyLite String Trimmer (UT21546). It starts up pretty easily (5 or 6 pulls) and runs fine after warming up. But after around 30 min or so it just dies. If I can get it started again (not guaranteed), it stalls out again in a minute or two. If I try again the next day, same story: start, run, stall after a while. I guess something is overheating but no idea what.
Any suggestions?
Thanks.