strcat breaks printf

[Wayne Gemmell <wayneg at ananzi dot co dot za>]

Hi all

I am writing my first embedded software on ecos. I am also new to C I'm a REAL 
newb. My problem is with the following code...

<code>
 smsBody = malloc(161);
        tmpStr = malloc(100);
        reset_log_read();
        smsBody = "tcc";

        puts("Hello");
        for (j=0;j < 1;j++)
        {
                tmpTime = rec->timestamp;
        puts("Hello");
                sprintf(tmpStr,";%d:%f:%f\0",(unsigned int) tmpTime, 
(float)rec->la,(float) rec->lo);
                printf("tmp : %s\n",tmpStr);
                strcat(smsBody,tmpStr);
        }

        puts("Hello");
</code>

And my output is as follows...

Hello
Hello
tmp : ;78453:-2614.993896:2822.247070
78453:-2614.993896:2822.247070
707078453:-2614.993896:2822.247070

This is the smsBody output from further on in the program.
tcc;78453:-2614.993896:2822.247070
So the above seems to work. I just don't understand the garbage output 
whenever I use puts or printf.

Could anyone give me any pointers?

Regards
Wayne Gemmell