possible bug in packageVersion()?

May be this problem is OS specific (mac OS or windows...) i use ubuntu and
have no problem with this function 
R> packageVersion("base")
[1] ?2.12.1?
R> packageVersion('lme4')
[1] ?0.999375.37?
R> sessionInfo()
R version 2.12.1 (2010-12-16)
Platform: x86_64-pc-linux-gnu (64-bit)

locale:
 [1] LC_CTYPE=fr_FR.UTF-8       LC_NUMERIC=C              
 [3] LC_TIME=fr_FR.UTF-8        LC_COLLATE=fr_FR.UTF-8    
 [5] LC_MONETARY=C              LC_MESSAGES=fr_FR.UTF-8   
 [7] LC_PAPER=fr_FR.UTF-8       LC_NAME=C                 
 [9] LC_ADDRESS=C               LC_TELEPHONE=C            
[11] LC_MEASUREMENT=fr_FR.UTF-8 LC_IDENTIFICATION=C       

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

other attached packages:
[1] ggplot2_0.8.9 proto_0.3-8   stringr_0.4   reshape_0.8.3
[5] plyr_1.4      MASS_7.3-9   

loaded via a namespace (and not attached):
[1] tools_2.12.1

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