fatal error: input in flex scanner failed – i’m starting to get mad…

hi all,

i’m at my first wordpress project at https://www.flasjobygden.org, a regional non profit organisation in a quite remot area in sweden.

however, all went just fine (well with the usual hassle) until today.

now, when i click one of the pages, the page builds up without the sidebar (no background either), and i get this error message:
———–
Fatal error: input in flex scanner failed in /home/net-havsnas/home.flasjobygden.org/public_html/wp-content/themes/iris on line 1
———–

i’m terribly sorry because i cannot tell you what i have done last that could have caused it. i worked with the sidebar.php to get in some plugins, and then i installed thomas boley’s mygallery. after that i got that message, but i dind’t check the pages since yesterday evening. so i have no clue where to look.

please help ??

thanks in advance