They look like large dust particles, I too, recommend using a blower brush without the brush on. If that doesnt work you could risk using one of the new CMOS cleaning kits around now in photographic shops but if u do follow the instructions exactly. Ive seen kits that consit of disposable sterile swabs (dust free) that you wipe once across the sensor then dispose of,single use so that dust collected doesnt cause scratching.
Here is some info on sensor cleaning
http://www.luminous-landscape.com/es...cleaning.shtml
some more at
http://www.bythom.com/cleaning.htm
When I change lenses I always point the camera down and do it as quickly as I can and preferably indoors or at least out of the wind to try and reduce chance of dust getting in.
I hope u get a speedy return to dust free imaging
Scott