I don't think x5 did this, i don't know about any setting that can do this. i would look to your webhost check there FAQ, i think they converted this somehow.....

unless you set every page seperatly in step 3 -> properties-> expert TAB

Else give them a call.

try to debug:

Are you sure you uploaded to correct folder server of your host? Has it worked earlyer?

if you export website to a folder on your harddrive, how are the files there