PAN: Need Help for Multiple Imputation Package

Hello all.  I am trying to run PAN, multilevel
multiple imputation program, in R to impute missing
data in a longitudinal dataset.  I could successfully
run the multiple imputation when I only imputed one
variable.  However, when I tried to impute a
time-varying covariate as well as a response variable,
I received an error message, ?Error: subscript out of
bounds.?  Can anyone tell if my commands contain any
mistakes?

First I imported SAS dataset ?sim? which includes a
response variable ?MIY1?, a time-varying covariate
?TCOV1?, TIME, GROUP (0 or 1), and ID.  200
participants were included and measurement occurred
six times.  Approximately 25% of participants dropped
out at end.      

sim <- read.xport('c:\\xptds.dat')

int <- rep(1,1200)
y <- cbind(sim$MIY1,sim$TCOV1)
subj <- sim$ID
pred <- cbind(int, sim$TIME, sim$GROUP)  

xcol <- 1:3
zcol <- 1

prior <- list(a=2,Binv=4,c=2,Dinv=4)

result <-

pan(y,subj,pred,xcol,zcol,prior,seed=13579,iter=1000)
Error: subscript out of bounds


By the way, I also received the same error message
when I tried to include intercept and time in Zcol, a
matrix for random effect specification.  I used
command ? zcol <- 1:2?.  Does anybody know if this
error is due to sample size/proportion of missing data
or due to command mistake?

I truly appreciate any feedbacks.
Best regards,
Eishi