Reviewing through your description it's possible the admin of your instance has configured specific files to be blocked in your instance. This can be checked via your admin console >> system >> settings >> documents/attachments tabs.
Additionally, if this does not resolve the beahvior I would recommend submitting a case in your secret customer group here in the Jive Community so that the next available support engineer can perform additional investigations into your specific instance. When creating the case if you could include a copy of the file you are seeing the error with along with a screenshot of the error you are seeing, this should assist with their investigation.
Thanks, can you please tell me how to find that customer group? I will check with the admin on the first part.