So when I'm using foobar2k to convert a music, if the destination directory is in d:\, the file results to be corrupted no matter --no-optimize is tagged or not. But if destination directory is in c:\ (not a network drive), the converted file is ok.
Could you try the following?
-V64 -o %d.m4a --log %d.txt -
If you set like this, output filename is different from what foobar2000 expects (extra ".m4a" is appended on the end). Therefore foobar2000 will show error, but the result will be actually in the destination folder, untouched by foobar side.
With --log option, log file will be written by qaac.
Also, console message of foobar2000 will be useful (view->console).