Quote - nruddock, your advice may be related to your personal/past experience, but you seem to be ignoring something here... all these folks (myself included) had this happen for the first time today/yesterday... this means that it's likely a common (externally influenced) cause.

I did not download/install anything (rarely ever download freebies ayway).  I tend to agree with pjz99 above - this sounds like something that happened over the network.

Agreed, but seeing the contents of the file will aid in determining what the cause might be.
If it isn't a bad character problem, then we need to attempt to determine what triggers it, be it a coding error in some file (freebie or otherwise), or something else common to the people who've suddenly starting getting this problem.