Hausman statistic cannot be calculated

Hi folks,

I tried running a panel procedure (RANTWO vcomp=fb), but the log shows the following error message:

"Hausman statistic cannot be calculated because different variables were dropped in the random effects model than in the fixed effects model."

The output shows:
Hausman Test for
Random Effects

DF m Value Pr > m

0 . .

Could any kind soul please advise on what went wrong and how to rectify this? Follow up reply from me is assured. Many thanks.