Website archive fails

[rjleaman]

I was successful in making a website archive via admin panel on December 30, and have changed no settings in site, browser, computer, or anything else I can think of that might have an impact - simply added content to the pages and uploaded some files. Today, however, when trying to do an archive, after a few seconds I'm taken to a blank page with URL http://example.com/admin/zip.php?s=long string of apparently random characters, and FTP shows no new zip in my zip folder.
Any thoughts on what might be going on here?
Thanks!