unable to parse .xt files made from xdebug php extension

Question

for some reason I'm able to create the outputfile inside my /tmp directory but the files aren't readable neither from kcachegrind or wcachegrind (the windows version)

php 5.3.6 xdebug 2.1.1

the file seems correct, here are the first two lines

TRACE START [2011-05-06 02:56:09]
0.0323     344532   -> {main}() /localhost/x/test.php:0

kcachegrind tells me that the file doesn't have the permission to be read (not true) wile wincachegrind tells me that its format is inconsistent and it has a parse error at some point.

any idea what can be wrong?