cffile action="write" not working

Hi all

im using the following code

<cffile action="write" file="#usersId#.txt" output="tewrasdfasdfasdf asdf a dsfa " nameconflict="OVERWRITE">

however it doesnt throw any errors, and doesnt create the file in short it does nothing

im using ms server 2008 and cf 10

can anyone shed any light on it

thanks