When you turn on the unit, it comes on fine and plays normally, then after about a minute it will turn off and the green light turns to read and the lamp light button will blink 4 times. I've cleaned the air filter and this does not seem to work, I'm unsure if it is a overheating problem or if the lamp/tube is bad, if it were the latter then how could the picture come up at all?

Thanks for any assistance or suggestions you may provide.

This post (http://www.avsforum.com/avs-vb/showthread.php?p=15780611#post15780611) seems to address your issue.