queXF 1.12.1 has been released today on Sourceforge
queXF 1.12.1 fixes a bug in the new ICR feature where during recognition, the thinning function failed due to a quirk in PHP global handling. ICR should be more accurate after applying this fix.
1. Backup config.inc.php (copy to config.inc.php.bak)
2. Extract the new package over your existing installation of queXF 1.12.0
3. Copy your config.inc.php.bak file over the extracted config file