Hi,

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.
https://www.centos.org/modules/newbb/viewtopic.php?topic_id=25878
http://wiki.centos.org/QaWiki/6/AuditStatus

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


--
Philippe Makowski
http://www.ibphoenix.com
Supporting users of Firebird
Tel +33 (0) 561058813