I had the same thing happen to a 2m x 3m office window whilst my desk was directly behind it.

To make matter worse it happened a few days after September 11 and it was on the top floor of our three level office.

It went off like a gunshot and made me fall off my chair and dive under the desk.

The glazier concluded the window glass was too tight in the aluminium frame and was restricted in it's expansion.

I certainly know it gave me one hell of fright. Almost needed a change of underwear. ooo

I would be checking the window is not too tight in the frame or the frame is out of alignment with the window.

See Dave Cavanaugh at French Connection for a replacement

French Connection
34 King St
Airport West VIC 3042
(03) 9338 8191

cheers

Rob