issues opening downloaded docx files from the internet on my mac air...

I have owned my Mac Air for nearly 1.5 yrs and never had an issue, until yestrday.

I can download docx files from the internet no problem, but when I go to open them (after they have saved into my downloads folder) a pop-up window with "convert file from" appears? Alas I can not open any downloaded docx files from the internet/email etc! This is making work very difficult.

Any suggestions would be greatly appreciated!