Open in chrome (not logged in, needs to be server from the cache) the contact form:
See the print screen. At the bottom strange binary content is rendered.
Only in chrome, works in firefox and safari.
1. Disable the gzip filter, problem gone.
2 or: server the form not form cache by adding ?something to the url, problem gone.
Seems its the combination that the cahche gzipes, and the gzip filter gzipes somehow also, or at least manipulates the http header wrong.