Firebird on Linux and ICU > 4.2
there was a bug in Firebird that did not handle well icu > 4.2 see (http://tracker.firebirdsql.org/browse/CORE-3447)
2.1.4 and 2.5.0 packages in distributions were affected (Debian, Fedora, Mandriva, Mageia) because they are using icu 4.4
Adriano fixed it and in these various distro updates are on the way
I know that some of you are using Centos 5.
The problem with Centos 5, is that you can’t have Firebird 2.5 from EPEL
repository. Centos 6 will give you the possibility to have Firebird 2.5 from EPEL6 repository, but seems that Centos6 take a long time to come.
You can try to use Scientific Linux instead (http://www.scientificlinux.org)
As Centos, the base SL distribution is basically Enterprise Linux
(RHEL), recompiled from source, and Scientific Linux 6.0 was released on
March 3, 2011