hi,
after reading alot of threads and documentation i decided to post, cause non of the found solutions worked for me.

Problem: after i compiled the plugin the app couldnt it load so i put the dll and some other dll to appdir and appdir/sqldriver. Now the app can load the driver connect to the server but crashes with a valid sql query an invalid like wrong table will be outputed as lasterror.

Okay now a bit more detailed:

Compiling the Plugin:
- Downloaded & Installed "qt-win-opensource-4.2.3-mingw.exe"
- Downloaded & Installed "postgresql-8.2.3-1.zip" (with setup)
- Downloaded & Extracted "postgresql-8.2.3-1-binaries-no-installer.zip" to c:\psql

Now i changed the following code
Qt Code: 
  1. cd %QTDIR%\src\plugins\sqldrivers\psql
  2. qmake -o Makefile "INCLUDEPATH+=C:\psql\include" "LIBS+=C:\psql\lib\ms\libpq.lib" psql.pro
  3. make
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to
Qt Code: 
  1. cd %QTDIR%\src\plugins\sqldrivers\psql
  2. qmake -o Makefile "INCLUDEPATH+=C:\psql\include" "LIBS+=C:\psql\bin\libpq.dll" psql.pro
  3. make
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Now compiling seems to work and the plugin is builded. After copying it over to appdir and some other .dll's from c:\psql\bin the app finds the plugin and crashes like described.

Sb. told me to backtrace the app with gdb i did and attached the output.
Source of my App is here: http://nopaste.info/79d8acca60.html

GDB Log can be found here:
http://www.file-upload.net/download-219057/gdb.txt.html

Hopefully sb. can explain me this strange behaviour , tuxi