R help - Feb 2012 - gmodels error: "no method for coercing this S4 class to a vector"

Dear All, 

I'm having a problem using functions in the gmodels library on an object of
class mer from the lmer package.  Code for a reproducible example is below.

# Load lme4 library and sample data 

library(lme4)
library(faraway)
library(gmodels)
data(penicillin)

# Fit a linear mixed effects model 

fit4 <- lmer(yield ~ treat + (1|blend), penicillin)

# Extract confidence intervals for fixed effects using gmodels library 

ci(fit4)

The call to 'ci' results in the following error:

Error in as.vector(data) : 
  no method for coercing this S4 class to a vector

This error does not occur when running the same code on R version 2.13.1.  Has
anyone else run into this problem?

Best regards, 
Tim Clough 

------- Session info below -------
> sessionInfo()
R version 2.14.1 (2011-12-22)
Platform: x86_64-pc-mingw32/x64 (64-bit)

locale:
[1] LC_COLLATE=English_United States.1252 
[2] LC_CTYPE=English_United States.1252   
[3] LC_MONETARY=English_United States.1252
[4] LC_NUMERIC=C                          
[5] LC_TIME=English_United States.1252    

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] gmodels_2.15.1   lme4_0.999375-42 Matrix_1.0-3     lattice_0.20-0  
[5] faraway_1.0.5   

loaded via a namespace (and not attached):
[1] gdata_2.8.2   grid_2.14.1   gtools_2.6.2  MASS_7.3-16   nlme_3.1-103 
[6] stats4_2.14.1 tools_2.14.1