Source: Joe Dellinger in The Risks Digest 14, 44 in 1993
Several months ago we started noticing that (now and again) the network connection to the mainland would become very very slow; this would continue for 10-15 minutes or so, then all would suddenly be well again. A while after this started happening a coworker of mine complained to me that the connection to the mainland never worked anymore. It seems that he had some FORTRAN source that he needed to copy to a machine on the mainland, but he never could because "the network wouldn't stay up long enough for the ftp to complete".
Yes, it turned out that the network outages happened whenever he attempted to ftp that particular FORTRAN source file to the mainland. We next tried compressing the file; it copied just fine then (but unfortunately the machine on the mainland had no uncompress program, so it was still no go). Finally we "split" his FORTRAN program up into very small pieces and sent them one at a time. Most of the pieces would copy without trouble, but a few would either not go at all or only go after many many retries.
Examining the troublesome pieces, we found they all had one thing in common: they contained comment blocks that began and ended with lines consisting of nothing but capital C's (his preferred FORTRAN commenting style). At this point we started sending e-mail to the network gurus on the mainland asking for help. Of course, they wanted to see an example of our un-ftp-able files, so we mailed some to them... but our mail never got there. Finally we got the bright idea of simply describing what the unsendable files were like. That worked. :-) [Dare I include in this message an example of one of the offending FORTRAN comment blocks? Probably better not!]
Eventually we were able to piece together the story. A new gateway had recently been installed between our part of campus and the connection to the mainland. This gateway had GREAT difficulty transmitting packets that contained repeated blocks of capital C's!!!! Just a few such packets would occupy all its energies and prevent most everything else from getting through. At this point we complained to the gateway manufacturer... and were told "Oh, yes, you've hit the repeated C's bug! We know about that already.". Eventually we solved the problem... by buying new gateways from another manufacturer. (In the manufacturer's defense I suppose an inability to propagate FORTRAN programs might be considered a feature by some!)