This happened to me many years ago. All of our sites (asp classic) on a single server went down at the same time. We had a library we shared across them all that handled some of the db interactions. We discovered that all of a sudden a sql query had the letter 'a' replaced with a 'q' (ie 01100001, vs 01110001).

I like to think my afternoon was sidetracked by cosmic radiation from millions of years ago :)