Error in "getClass" when calling the function "show"

Dear List,

Calling "show" on an object of class "summary.lm" gives:
Error in getClass(class(object)) : "summary.lm" is not a defined class

Is this a miss on my end ?

x <- seq(1, 10)
show(x)

[1]  1  2  3  4  5  6  7  8  9 10

y <- runif(10)
fit <- lm(y ~ x)
show(fit)

Call:
lm(formula = y ~ x)

Coefficients:
(Intercept)            x
   1.04938     -0.08869

show(summary(fit))

Error in getClass(class(object)) : "summary.lm" is not a defined class

class(summary(fit))

[1] "summary.lm"

class((fit))

[1] "lm"

getClass("lm")

Virtual Class

No Slots, prototype of class "S4"

Extends: "oldClass"

Known Subclasses:
Class "mlm", directly
Class "aov", directly
Class "glm", directly
Class "maov", by class "mlm", distance 2
Class "glm.null", by class "glm", distance 2

getClass("summary.lm")

Error in getClass("summary.lm") : "summary.lm" is not a defined class

sessionInfo()

R version 2.7.0 Patched (2008-06-07 r45877)
i686-pc-linux-gnu

locale:
LC_CTYPE=en_US.UTF-8;LC_NUMERIC=C;LC_TIME=en_US.UTF-8;LC_COLLATE=en_US.UTF-8;LC_MONETARY=C;LC_MESSAGES=en_US.UTF-8;LC_PAPER=en_US.UTF-8;LC_NAME=C;LC_ADDRESS=C;LC_TELEPHONE=C;LC_MEASUREMENT=en_US.UTF-8;LC_IDENTIFICATION=C

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


Laurent