QFile resized files gets truncated after writing

[MaximA]

Hi ppl,

I wrote some code to generate a file with a specific size, in which I later put QByteArrays at specific positions (random-acces).

...
file.resize(1024000);
...
file.seek(12335);
pos = file.pos();
c_size=file.write(ba);
pos2 = file.pos();
file.close();
...
//QT4.3 / mingw / windows xp

...
file.resize(1024000);
...
file.seek(12335);
pos = file.pos();
c_size=file.write(ba);
pos2 = file.pos();
file.close();
...
//QT4.3 / mingw / windows xp

To copy to clipboard, switch view to plain text mode 

the initial QFile::resize works
pos and pos2 indicate the right position

after closing the file it is truncated

Any help/idea is highly appreciated, after having exhausted my resources.
Thanks in advance