Error: WorkBench Error: Could not register files of type:Udf
 

As the title, I have an error after initializing (it is still ok), but after running calculation it appears.
"Error: WorkBench Error: Could not register files of type:Udf"
error photo: http://i62.tinypic.com/16q51u.png
I think the problem is at the begining, with FILE *fid. I can not write this file.
here's my code :

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#include "udf.h"

FILE *fid;

DEFINE_PROFILE(flux_setget,t,i)
{
face_t f;
int zoneid = THREAD_ID(t);

/* Write the property and thread id values for the flux condition to file */
fid = fopen("flux-ids", "w");
fprintf(fid, "%d, %d\n", zoneid, i);
fclose(fid);

/* Set initial profile values */
begin_f_loop(f,t)
{
F_PROFILE(f,t,i) = 10;
}
end_f_loop(f,t)
}

DEFINE_ADJUST(flux_adjuster, domain)
{
int iprop;
int izone;
int n = 0;
Thread *t;
face_t f;
Thread *c_thread;
cell_t c;
real pressure = 1;
real newvel;

/* Read in the property and thread id values stored by the BC UDF */
fid = fopen("flux-ids", "r");
fscanf(fid,"%d, %d", &izone, &iprop);
fclose(fid);


thread_loop_c(c_thread, domain) /*loops over all cell threads in domain*/
{
/* Loop over cells in a thread to get information stored in cells. */
begin_c_loop(c, c_thread)
{
/* C_T gets cell temperature. The += will cause all of the cell
temperatures to be added together. */
pressure += C_T(c, c_thread);
n = n+1;
}
end_c_loop(c, c_thread)
}
pressure=pressure;

/* Get the thread pointer based on the obtained zone id */
t = Lookup_Thread(domain, izone);
/* Read the needed data, then calculate and set the new flux values */
begin_f_loop(f,t)
{
if (pressure < 330)

newvel = 0;

else



newvel = sqrt(2*(fabs(pressure))/1.225);

F_PROFILE(f,t,iprop) = newvel;
}
end_f_loop(f,t)
}


DEFINE_PROFILE(unsteady_pressure, thread, position)
{
face_t f;
real t = CURRENT_TIME;

begin_f_loop(f, thread)
{
F_PROFILE(f, thread, position) = 5 + 4*sin(6.28* t);
}
end_f_loop(f, thread)
}