Unique operator error w/ concatenation

Folks, experiencing an odd issue. The following on an 8.4 server: select 'foo'::text || 123

Blows up, saying:

ERROR:  operator is not unique: text || integer
LINE 1: select 'fo'::text || 123;
                          ^
HINT:  Could not choose a best candidate operator. You might need to add explicit type casts.

But on another postgres 8.4 server, it properly returns a concatenated string.

Any tips on how/where I can track down why/where there might be duplicate operators?

--
Wells Oliver
Architect, Baseball Systems
619-795-5359
San Diego Padres | 100 Park Boulevard | San Diego CA 92101