Often when i begin a flight using one of my PMDG 737's i will go to enable the Autothrottle and it wont turn on and the middle warning light flashes A/T P/mnt or somthing i think its called.What am i doing wrong that causes this?

Very common problem, check that engine generators are on line. See PMDG OPS wiki library FAQs

Ms/Mr Nameless,Please sign your posts with your name as per the forum rules.Maybe this will help you with your problem:http://ops.precisionmanuals.com/wiki/PMDG_..._will_not_latchHope it helps,