Buttons not diplaying text

Hello.

I’m experiencing a really weird issue.
I cannot get the buttons in the registration and login forms to show the “Login” and “Register” texts.

I just get empty boxes. When I write something else, for example registerrrr or loginnnn, it works. I think the default words have been overwriten somehow somewhere and UM does not allow them to be shown.

Here’s the comparison screenshots so you can take a look:

https://s1.postimg.org/iadlpvdxb/capture1.jpg
https://s18.postimg.org/d42zrjfe1/capture2.jpg

I wanted to ask you another thing, irrelevant to the above.
I want to change the “Confirm Password” text to say something completely different, for example “Type your password again”. Can this be done?
Here’s a screenshot:
https://s32.postimg.org/6vfnny34l/capture3.jpg

So please let me know.
Thank you.