I also have this same problem,
I however only replaced the DC Jack itself not the entire Power Module,
but my Dell Inspiron 1545 does the same thing, it will power up automatically after removing the cmos battery and clearing the cmos,
it will power down properly but will not turn back on unless doing the same thing "clearing the cmos"
any help would be greatly appreciated as I really do not want to junk out this fairly decent laptop,
Thank you ,