Different sort order

I'm wondering why the sort order on these two servers behaves differently.
The only difference I can see is that one is using a 32.bits Ubuntu and
the other is on 64bits versions of Ubuntu.
But why this difference ?

Thanks,
Poul

mydb=# select * from test order by felt1;
felt1
--------
test1
test_1
test2
test_2
test3
test_3
(6 rows)

mydb=# \encoding
UTF8
mydb=# select version();

version
------------------------------------------------------------------------------------------------------------
PostgreSQL 8.1.9 on i486-pc-linux-gnu, compiled by GCC gcc-4.0.gcc-opt
(GCC) 4.0.3 (Ubuntu 4.0.3-1ubuntu5)

mydb=# select * from test order by felt1;
felt1
--------
test1
test2
test3
test_1
test_2
test_3
(6 rows)

mydb=# \encoding
UTF8
mydb=# select version();

version
--------------------------------------------------------------------------------------------------------------
PostgreSQL 8.1.9 on x86_64-pc-linux-gnu, compiled by GCC
gcc-4.0.gcc-opt (GCC) 4.0.3 (Ubuntu 4.0.3-1ubuntu5)
(1 row)