I've had the same problem. At work the COW didn't function, but at home it worked fine, so I did this:
Get a fresh buff-in.rc5 from the keyserver using your home pc. Copy this buff-in to a floppydisc. Now let your COW at home get a new buff-in again and let it work.
Now go to your work pc and copy the buff-in from your floppy to the directory where you installed the COW (distributor). Start your COW and see; is has buff-in so it'll work.
After you have completed say 50 packets copy the buff-out.rc5 from your work pc to the floppy and delete the old one in the COW directory at your work address. Now this buff-out is empty and you can let it work again.
Now go to your home pc and let your COW flush it's work. Delete the buff-out (AFTER FLUSHING!!!) and then copy the buff-out from your floppy to the directory where you installed the COW. Now let it flush again...
Done. It takes some work, but after you've done it once it will only go faster the second time
For more info visit the RC5Forum:
Redneck and Badtobone will help you.