Occasionally Dim Scree - nightmare to test!

Got a Toshiba Satellite Pro 1110 here where occasionally the screen goes very dim. The guy who owns it says it keeps happening at odd times, I had to keep turning it on and off over the course of 2 days to get the screen to go dim!
I disassembled the laptop and screen, checked all the connections from the mobo to the inverter and etc (took the inverter out and reconnected it).
The laptops now on with the screen looking fine so I'm just gonna leave it on indefinitely until it goes dim again (assuming my reconnecting hasn't fixed it).

Does it sound like an inverter problem or is intermittent failure a sign of something different?

The prices of replacement inverters vary quite significantly off ebay
http://cgi.ebay.co.uk/NEW-Toshiba- [...] 53dd931ac8
£39
http://cgi.ebay.co.uk/TOSH-INVERTE [...] 5633e19f9d
£16
http://cgi.ebay.co.uk/TOSHIBA-1110 [...] 2556ef6793
£25

but i only want to get one if I'm sure this is what it is! I just want to make sure its not the backlight. I could always plug a similar LCD screen in off another laptop and see if the same dimming happens.

What does everyone think? should I just spend the £20+ and get a new inverter?

Much thanks for your time,
Dan Gent