Getting blue spots on longer exposed images?

Hey everyone,

When i expose my images usign the D100 at night, for say 1.5 seconds exposure, some blue dots appear on the frames. For just small exposures this is fine and i can photoshop them out because there isn't many of them. But when I make a longer exposure on BULB and so on more bluespots appear, almost as if its noise adding to the picture, but iwouldnt expect this sort of noise with a digital SLR camera?!

I was wondering if I needed to get the CCD professionally cleaned or something. I had it recently blow-cleaned and cleaned with that 'pen cleaner' item that you can use for cleaning the CCD.

Any advice would be much appreciated!

Thanks very much in advance,

Niall