Interesting, I can't replicate this.  Perhaps it has to do with package versions
(of other attached packages?):
> sessionInfo()
Version 2.3.0 (2006-04-24)
x86_64-unknown-linux-gnu
 
attached base packages:
[1] "tools"     "methods"   "stats"     "graphics"  "grDevices" "utils"
[7] "datasets"  "base"
 
other attached packages:
ontoElicitor      Biobase         RBGL        graph        Ruuid
     "0.0.4"     "1.11.0"      "1.6.0"     "1.11.0"      "1.9.2"