Stainless Steel Kenmore Elite 36 in. 2.0 cu. ft....

Question

Stainless Steel w Kenmore Elite 36 in. 2.0 cu. ft. Microhood Combination Model 63763Have had this since 10/04 love it! But just today when I went to use it to warm up my tea for a minute it stopped at 53 seconds (I've done this many times over!) always stops at 53 seconds! weird for some reason! Then on display panel it shows F-9. Any ideas let me know ASAP ! Thanks!