Dell 3110cn - blue streaking on right hand side

[TRM]

Hi, I'm getting blue streaking on the paper on the right hand side. When I look at the blue print cartridge, there is about a 1cm wide residue of blue toner on the left hand side of the drum as you are looking at it when in place (not sure if that is the correct name for that part on the cartridge).

Any ideas how I can fix this?

Thanks

TRM