Sounds more like you got coolsearch, sasser, soBig, myDoom and netsky all bundled up together. Do you have a firewall? You might want to invest on a good one if you are running a business. A physical firewall, a software one of the pC and an updated AV seems to do the trick for me...you should try it.
The attacks themselves start with hijacking my browser, then my Stop Sign AV programs are crippled so that I cannot delete the infected files. Then comes the knockout blow. This happens over a period of 5 - 10 days. The last time I couldn't turn my monitor on, or turn off the machine with the front panel button - I had to pull the power cord.