Unreliable data stream
C, 168 characters

i;main(c){for(srand(&amp;c);i++&lt;3;putchar(rand()%10?i=0,c:c-126?c+1:33))c=getchar();
puts("ERROR CODE 4625: UNRECOVERABLE ERROR, PLEASE CONTACT YOUR SYSTEM ADMINISTRATOR");}


This solution's seeding of the PRNG takes advantage of the fact that modern OSes change the stack's location in memory on each run, as a basic measure against stack-smashing exploits.