No code has changed with ACARS in 3 weeks:
http://bugs.phpvms.net/log/trunk/core/modules/ACARS/ACARS.php?rev=815
http://bugs.phpvms.net/log/trunk/core/modules/ACARS/fsacars.php?rev=815
http://bugs.phpvms.net/log/trunk/core/common/ACARSData.class.php?rev=815
It was probably a corrupt file on upload, or something on your end. I'll still double check against the dev site, but Joeri and several others would have noticed if it was a core issue.
Again, find that old thread, it's your HTML code. Re-download your ACARS config file as well, and reinstall FSACARS from scratch (delete the folder and completely reinstall).
Hopefully I'll get some time this weekend to check