IBASE driver not found ?

[jacek]

Looks like the previously installed version.

ldd sqlbrowser
linux-gate.so.1 => (0xffffe000)
libQtSql.so.4 => /usr/lib/libQtSql.so.4 (0xb7e8a000)
libQtGui.so.4 => /usr/lib/libQtGui.so.4 (0xb77b8000)

Yes, in such case Qt might not want to load any plugins from the newer version because of mismatching build keys.

Recompile your application using the new Qt version. If you use qmake, simply run qmake from /usr/local/Trolltech/Qt-4.2.3/bin on your .pro file, then "make clean" and "make".