Damyan Ivanov announced :

I have prepared packages from the current version in wheezy

(2.5.1.26351), built for squeeze.

ftp://ftp.modsoftsys.net/public/firebird2.5-backports/

If these improve the situation, then we at least know the bug is fixed

in that version and can start looking for the exact fix, which would

take about 10 iterations (and probably several weeks).

[ED if you want to rebuild them for 32bits you can use these instructions ]