Please try to upgrade to 0.12.1-2, as changelog specifies:
$ zcat /usr/share/doc/psi/changelog.Debian.gz | head -n 10
psi (0.12.1-2) unstable; urgency=low
* Build-depend on qt >= 4.5.1
This should fix an incompatibility between binaries compiled with
older qt versions and newer shared library versions. (Closes: Bug#526335)
* Conflict with libqca2 << 2.0.2, as older qca versions cause
problems with qt 4.5.
* Update Standards-Version
Regards,
Robert