R help - Feb 2004 - polr warning message optim

Hello R-users,
I am using polr function in library(MASS). The code I use is the following:

polr(as.ordered(q23p)~.,data=as.data.frame(datapr2))

where datapr2 is a matrix of 63 columns (together with the dependent 
variable) and 1665 rows. But I am receiving the warning message Error in 
optim(start, fmin, gmin, method = "BFGS", hessian = Hess, ...)

I would be very greatfull if anyone could suggest something.
Thank you