Dark Screen

Hey all,

 

I'm hoping someone will 1) be able to identify what is happening and 2) provide some help so I can stop it happening. Here's the story:

 

When I have my laptop (Inspiron 1000, purchased late 2004) in sleep mode and start it up, 1 of 2 things will happen - 1) If plugged in, it starts up normally (not the problem); 2) if running on battery power, it starts up but the screen is either black or so dark as to be virtually unreadable (the problem).

 

Occasionally, the screen will also go dark if I have it running on battery, but I'm nowhere near the end of the battery (I'm conscientous about checking).

 

Any ideas out there? Anyone? Anyone? Thanks in advance.