The AT website lists the CM5 as a discontinued model of the 4050. The 4050 is still manufactured and sold but not the cm5 version. I don't know the difference though. I have two 4050s that I use pretty regularly.
The AT4050 is the first 'more expensive' mic that I really saw the value in - you can't get a nice sound like that from a cheap mic! It's a great, versatile mic with a slight lift in the highs which works great with most acoustic instruments and vocals.
thanks alot guys .. i bought one on ebay for 400 with a shockmount and box .. brand new, pretty sweet. but yeah i bought it a couple of days ago it was from a ebay store and it wasnt the cm5 version. my m-audio tampa arrived today