R help - Feb 2013 - slotName defined in object, present in instance, but inaccessible [SCL:4]

from a package I'm writing....

##setClass('Occupancy',contains="DataFrame",
##                 representation(states="StatesORNULL"))
##
R> foo <- occupancy(pooledMethSegs)
R> plotOccupancy(foo)
Error in slot(object, "states") :
  no slot of name "states" for this object of class
"Occupancy"
R> slotNames(foo)
[1] "states"          "rownames"        "nrows"   
"listData"
[5] "elementType"     "elementMetadata" "metadata"
R> foo@states
Error: no slot of name "states" for this object of class
"Occupancy"


Any ideas as to what's going on here?


R> sessionInfo()
R Under development (unstable) (2013-01-29 r61783)
Platform: x86_64-unknown-linux-gnu (64-bit)

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

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

other attached packages:
 [1] rtracklayer_1.19.9    chromophobe_0.49      pheatmap_0.7.4
 [4] ggplot2_0.9.3         reshape2_1.2.2        GenomicRanges_1.11.28
 [7] IRanges_1.17.31       BiocGenerics_0.5.6    BiocInstaller_1.9.6
[10] gtools_2.7.0          devtools_1.0

loaded via a namespace (and not attached):
 [1] Biostrings_2.27.10 bitops_1.0-5       BSgenome_1.27.1
 colorspace_1.2-1
 [5] dichromat_2.0-0    digest_0.6.2       evaluate_0.4.3     gtable_0.1.2

 [9] httr_0.2           labeling_0.1       lattice_0.20-13    MASS_7.3-23

[13] Matrix_1.0-10      memoise_0.1        munsell_0.4        plyr_1.8

[17] proto_0.3-10       RColorBrewer_1.0-5 RCurl_1.95-3
Rsamtools_1.11.15
[21] scales_0.2.3       stats4_3.0.0       stringr_0.6.2      tools_3.0.0

[25] whisker_0.1        XML_3.95-0.1       zlibbioc_1.5.0

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