i got the same problem here...

my N900 is about 2 weeks old..
i charged it many times..
but today.. i plugged it in at my PC, but nothing happend,
no green light, no messages appears at N900...

i tried another cable, another PC, and than i tried it with the 230V - Charger...
but.. nothing..

i removed the battery, waited for 5 min, tried again.. nothing..

so.. any ideas?

- M4dMike