Description of problem:
The problem is easy to reproduce, just try the following:

robert@tux:~ > LANG=C cp /boot/memtest86+-1.65 /etc
cp: cannot create regular file `/etc/memtest86+-1.65': Permission denied
robert@tux:~ >

robert@tux:~ > LANG=de_DE@euro cp /boot/memtest86+-1.65 /etc
Speicherzugriffsfehler
robert@tux:~ >

"Speicherzugriffsfehler" means "segmentation fault" in English. For me, it 
looks like that you can reproduce it with any application using gconv or so?
For example, chowns or chmods which should end up in a localized "Permission 
denied" also have a "segmentation fault" when using another LANG env.

I guess the same bug caused my chat client irssi to core dump:
#0 0x00410abe in __gconv_transliterate (step=0x8de13b4, step_data=0x8bc9814, 
trans_data=0x0, inbufstart=0x8e73000 ":", inbufp=0xbff7b948, 
inbufend=0x8e73024 "f", outbufstart=0xbff7b94c, irreversible=0xbff7b954) at 
gconv_trans.c:207 
207 gconv_trans.c: No such file or directory. 
in gconv_trans.c

#0 0x00410abe in __gconv_transliterate (step=0x8de13b4, step_data=0x8bc9814, 
trans_data=0x0, inbufstart=0x8e73000 ":", inbufp=0xbff7b948, 
inbufend=0x8e73024 "f", outbufstart=0xbff7b94c, irreversible=0xbff7b954) at 
gconv_trans.c:207 
#1 0x009527ed in gconv (step=0x8de13b4, data=0x8bc9814, inptrp=0xbff7ba10, 
inend=0x8e73024 "f", outbufstart=0x0, irreversible=0xbff7ba88, 
do_flush=0, consume_incomplete=0) at ../iconv/loop.c:311 
#2 0x0040f0d3 in __gconv_transform_utf8_internal (step=0x8de1378, 
data=0x8bc97f0, inptrp=0xbff7bad0, inend=0x8d4801d "", outbufstart=0x0, 
irreversible=0xbff7ba88, do_flush=0, consume_incomplete=0) at ../iconv/skeleton.
c:674 
#3 0x00409d03 in __gconv (cd=0x8bc97e8, inbuf=0xbff7bad0, inbufend=0x8d4801d "", 
outbuf=0xbff7bacc, outbufend=0x89c5451 "", 
irreversible=0xbff7ba88) at gconv.c:72 
#4 0x0040933a in iconv (cd=0x8bc97e8, inbuf=0xbff7bad0, inbytesleft=0xbff7bad8, 
outbuf=0xbff7bacc, outbytesleft=0xbff7bad4) at iconv.c:53 
#5 0x00550bbe in do_conv (obj=0x8c490b8, string=0x8c3a2a0) at Iconv.xs:112

Version-Release number of selected component (if applicable):
glibc-2.3.90-22
gcc-4.1.0-0.10

How reproducible:
Everytime, see above.

Actual results:
Segmentation faults :-(

Expected results:
Just working again soon... ;-)