R help - Nov 2010 - rbind error (maybe a problem with chron package?)

Hello,

I have a list of data frames that I would like to combine to a single
data frame.  I typically do this with:
do.call(rbind, list.of.dataframes)

This time, I get
Error in class(x) <- cl : 
  cannot set class to "array" unless the dimension attribute has
  length > 0

I'm not sure what's happening.  Each data frame has a column of chron
objects and a column of float values.  Minimal example of the data
frames and the error below.  If I start with a fresh R session, it
works, until I load the chron package.

I'd appreciate any suggestions!

Thanks,
Tim

--

Timothy W. Hilton
PhD Candidate, Department of Meteorology
The Pennsylvania State University
503 Walker Building, University Park, PA   16802
hilton at meteo.psu.edu


--------------------------------------------------
foo <- structure(list(date = structure(c(12052.75, 12052.875, 12053, 
12053.125, 12053.25, 12053.375), .Dim = 6L, format
structure(c("m/d/y",
"h:m:s"), .Names = c("dates", "times")), origin =
structure(c(1,
1, 1970), .Names = c("month", "day", "year")),
class = c("chron",
"dates", "times")), val = structure(c(NA_real_, NA_real_,
NA_real_,
NA_real_, NA_real_, NA_real_), .Dim = 6L)), .Names = c("date", 
"val"), row.names = c(NA, 6L), class = "data.frame")
--------------------------------------------------

and an example of the error:

--------------------------------------------------
> foo
foo
                 date val
1 (12/31/02 18:00:00)  NA
2 (12/31/02 21:00:00)  NA
3 (01/01/03 00:00:00)  NA
4 (01/01/03 03:00:00)  NA
5 (01/01/03 06:00:00)  NA
6 (01/01/03 09:00:00)  NA
> rbind(foo, foo)
rbind(foo, foo)
Error in class(x) <- cl : 
  cannot set class to "array" unless the dimension attribute has
  length > 0
--------------------------------------------------

If I start with a fresh R session, it works, until I load the chron
package:

--------------------------------------------------

$ R --vanilla

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Copyright (C) 2010 The R Foundation for Statistical Computing
ISBN 3-900051-07-0
Platform: x86_64-unknown-linux-gnu (64-bit)

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Type 'license()' or 'licence()' for distribution details.

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> foo <- structure(list(date = structure(c(12052.75, 12052.875, 12053,
+ 12053.125, 12053.25, 12053.375), .Dim = 6L, format
structure(c("m/d/y",
+ "h:m:s"), .Names = c("dates", "times")), origin
= structure(c(1,
+ 1, 1970), .Names = c("month", "day", "year")),
class = c("chron",
+ "dates", "times")), val = structure(c(NA_real_, NA_real_,
NA_real_,
+ NA_real_, NA_real_, NA_real_), .Dim = 6L)), .Names = c("date",
+ "val"), row.names = c(NA, 6L), class =
"data.frame")
> foo
      date val
1 12052.75  NA
2 12052.88  NA
3 12053.00  NA
4 12053.12  NA
5 12053.25  NA
6 12053.38  NA
> rbind(foo, foo)
       date val
1  12052.75  NA
2  12052.88  NA
3  12053.00  NA
4  12053.12  NA
5  12053.25  NA
6  12053.38  NA
7  12052.75  NA
8  12052.88  NA
9  12053.00  NA
10 12053.12  NA
11 12053.25  NA
12 12053.38  NA
> library(chron)
> rbind(foo, foo)
Error in class(x) <- cl :
  cannot set class to "array" unless the dimension attribute has
  length > 0