R help - Sep 2009 - question on a warning(?) message from glm poisson regression

Hello,
   I got the following message after fitting the poisson regression
using the glm function.
Are the results (coefficient estimates, their stderr, deviance,
predicted values...) reliable? Can I still go on and interpret them?
 How much caution should I exercise for these results with this message?


##########
 > mmm6 <-glm(freq~x+y+x.2+y.2+x.3+y.3+x.4+y.4+x.5+y.5+x.6+y.6+xy
,family=poisson(link = "log"),data=ddd2)
Warning message:
In glm.fit(x = X, y = Y, weights = weights, start = start, etastart etastart,  :
  fitted rates numerically 0 occurred
##########

  Thank you so much,
  Insu Paek

*************************************************
Insu Paek 
Educational Testing Service
Rosedale Road MS - 02P
Princeton, NJ 08541
(Tel) 609 - 734 - 1450 
Email: ipaek@ets.org 
*************************************************




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