Extreme slowdown with named vectors. A bug?

Another example:

avec <- 1:55000
names(avec) <- as.character(avec)
system.time(avec[names(avec)[1:39045]])

[1] 0.06 0.00 0.07   NA   NA

system.time(avec[names(avec)[1:39046]])

[1] 23.89  0.00 23.94    NA    NA

version

_
platform       i386-pc-mingw32
arch           i386
os             mingw32
system         i386, mingw32
status
major          2
minor          4.0
year           2006
month          10
day            03
svn rev        39566
language       R
version.string R version 2.4.0 (2006-10-03)


FWIW, this example shows similar behavior on R-2.2.0 Linux.

Tried the following with R --vanilla on the Rv2.4.0 release (see
details at the end).  I think the script and its comments speaks for
itself, but the outcome is certainly not wanted.

[snip]


Charles C. Berry                        (858) 534-2098
                                          Dept of Family/Preventive Medicine
E mailto:cberry at tajo.ucsd.edu	         UC San Diego
http://biostat.ucsd.edu/~cberry/         La Jolla, San Diego 92093-0717