Problems displaying formula - "x" to the power of

[Lech]

Hi, I can display the above formula, but I can't stop from appearing a rectangular frame that
surrounds it. I'm running O.O.3.3 with Windows 7 Ultimate x86. The path I'm using to insert
the formula is such: Insert > Object > Formula, then in the bottom window I enter: x^y which
shows (in that window) without any extra signs/characters and once entered, forms a
dark rectangular frame. I tried, right clicking on the formula (in document) choosing - Object
from the drop down menu, than - Borders tab, where the Style is selected as 0.05 pt. When
I choose - "none", click OK, reopen it - it is back to the 0.05 pt. Also in the Line arrangement,
when I try to set the No Borders option, I expect a check mark to show and there is none.
Am I missing something?