Dynamic C 9.25 FAT problems

Hi group.
I'm writting a program to get a fix long events log.

I can open the file and execute functions (fat_Read, fat_Write, fat_FileSize and anothers) , but sometime the programs not works. The variables are changed with random values. In anothers although set a variable to some value ( i=0), after that the program execute this line, the variable is not setting. I have carrefully with the string lenght variables and whith variables types.
. 
It is more. In a program, the fat_Close(..) return invalid handle. I have save the same program with another name, and fat_Close (..) works well. !!!

I use the same computer to program the RCM 3700 ussing rabbit web and another libs, and not get any problem.

Is there some problem with fat.lib ???

Wait for yours comments and thanks in advance.

Omar