Boot problem from standby - Leopard MacBook Pro

[SL91]

First post on this forum, so I hope this is the right place for this query.
I'm running a Macbook Pro that is about 7 month old (purchased 26 Nov last year). It gets a fair amount of work, but not enough that it should really be taxing the system, main uses are (right now) word processing and a little bit of graphics work. However, its developed and annoying habit of failing to reboot from standby. It will boot to the login screen, then, upon my entering the password, the screen will go blank and nothing else will happen. The only way to get it to work is to shut-down and reboot using the power button. It developed this problem whilst I had Boot Camp installed and I thought that was what was causing it. But alas, uninstalling Boot Camp has not fixed the problem.

Anyone have any ideas?

Cheers
SL91

EDIT:
Details: MBP, Leopard 10.5.2, 2.6 Ghz, 4GB Ram, otherwise standard.