Does your frame have horizontal rear dropouts - if so, install a chain tug such as the Surly Tuggnut http://surlybikes.com/parts/tuggnut - there are several options on the market.
Then mess with the tension so that your chain only has about 1/8 to 1/4 inch of play.
You might also want to install a chainwatcher on your seattube to help prevent it falling off the chainrings. K-Edge and Paul make expensive ones... but I just use the Third Eye which costs like 10 bucks. Ugly but functional.
If you don't have a horizontal dropout then you need a chain tensioner or an eccentric hub. IMHO, chain tensioners are crap for CX racing.
Finally, this magazine ran a good story about SSCX rigs in one of its early issues. You should search that out.
thanks...if I go with a chain ring guard, do I order the same size as my chain ring (36t) or something bigger?
Same size. I have two from these guys http://www.bbgbashguard.com/
Hand made in USA, great quality, and good price.
tried the BBG chain guard and the third eye. works fine. thanks...did 30 miles today
Glad that worked for you! Are you using the chain tug?
no to chain tug--just chainring guard and third eye. working fine now