R help - Sep 2008 - problems with too many NA in the function ideal() from pscl package.

Hi all,

I'm trying to run some monte carlo simulation for my roll call data
using the ideal() function, which resides in the pscl package.
However, I'm receiving an error message that I don't understand.

Error in ideal(a, maxiter = 1000, thin = 10, burnin = 50, store.item = TRUE,  :
  NA/NaN/Inf in foreign function call (arg 13)


my code is simple the following:

> m_a <- ideal(a, maxiter = 1000, thin = 10, burnin = 50,
+ 			   store.item = TRUE,  normalize=T,
+ 				priors=list(xp=1e-12,xpv=1e-12,bp=1e-12,bpv=1e-12), verbose=T)
ideal: analysis of roll call data via Markov chain Monte Carlo methods.

Subsetting rollcall object a using dropList
Using the following codes to represent roll call votes:
Yea:		 1
Nay:		 0
Abstentions:	 NA
Not In Legislature:	 9

Ideal Point Estimation

Number of Legislators		 30
Number of Items			 1172

checking for any user-supplied priors...

checking start values...
will use eigen-decomposition method to get start values for ideal points...done
running 1172 vote-specific probit GLMs
 for start values for item/bill parameters
 conditional on start values for ideal points...done
using the following start values for ideal points (summary follows):
       V1
 Min.   :-0.7573
 1st Qu.:-0.1583
 Median : 0.0000
 Mean   :-0.0342
 3rd Qu.: 0.0000
 Max.   : 0.8160
using the following start values for item parameters (summary follows):
       V1                  V2
 Min.   :-131.2397   Min.   :-49.27293
 1st Qu.:  -1.9090   1st Qu.: -1.33518
 Median :  -1.5156   Median : -0.34876
 Mean   :   0.5443   Mean   : -0.07001
 3rd Qu.:   1.6978   3rd Qu.:  1.22064
 Max.   : 553.5285   Max.   : 65.19820
 NA's   : 573.0000

Starting MCMC Iterations...
Error in ideal(a, maxiter = 1000, thin = 10, burnin = 50, store.item = TRUE,  :
  NA/NaN/Inf in foreign function call (arg 13)
+


The problem, I think, is that many data matrix has too many NA. Does
anybody have any suggestion?

Thanks in advance,

Antonio.