[R] puzzling lm.fit errors

[Brendan Morse]

Hi everyone, I am running a monte carlo and am getting an error that I  
haven't the slightest clue where to begin figuring it out. The error  
is as follows:

Error in lm.fit(x, y, offset = offset, singular.ok = singular.ok, ...) :
   0 (non-NA) cases
In addition: Warning message:
In ltm.fit(X, betas, constraint, formula, con) :
   Hessian matrix at convergence is not positive definite; unstable  
solution.


The puzzling aspect though is that it successfully runs a number of  
complete iterations before this occurs. I am not sure what or where  
this is going on.

Any suggestions?

Thanks very much (in advance)
- Brendan