[development] blank screen at line 1

[Lluís]

while developing a module, I have just started to recieve white screen
every time I submit a form (besides form gets submited).

In some cases I have been able to see this error:
warning: Cannot modify header information - headers already sent by
(output started at
/var/www/ccc/sites/all/modules/comptacau/comptacau.module:1) in
/var/www/ccc/includes/common.inc on line 141.

but I file comptacau.module have no white spaces at start. Any hint of
how to track this problem?

thanks

PS: memory limit is set to 256 just in case it was a memory problem,
but apache reports no problem with memory.


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