I am not sure what Inline Cells are, but here's an experiment I just did after reading your reply:
I created a new notebook, and copy/pasted one of the examples of the Plot function from the Mathematica documentation directly into my notebook, and used it to create a plot. I then clicked the "themes" and "labels" buttons, and everything worked fine, the program did not hang.
Then I went back to the notebook where I was having this problem. I confirmed that the problem still exists in that notebook - clicking themes or labels or axes causes the program to hang.
Then I made a another new notebook. I copied ONLY the function I was having problems from my old notebook into this new notebook. It was very simple, something along the lines:
v[a_] := ((u * m)/(r + a))^0.5
Plot[v[a], {a, 100, 100000}]
where u/m/r are variables that have already been initialized with appropriate values. In my old notebook, they had values that had been calculated earlier, but for the test, I just initialized them with sample values.
This time when I clicked on themes/plot/axes, it worked, there was no program hang.
So there is something in my original notebook that is causing the problem. It's a pretty large notebook. I'd like to troubleshoot it and see if I can find the problem, but I'm not sure where to begin.
Like I said, I don't know what Inline Cells are, but there are certainly a lot of text cells in the notebook - I like to add text commentary everywhere to document what I'm doing and sometimes even copy/paste from textbooks or the web directly into the notebook. Some of the text has formulas embedded, I wonder if those might be what you're referring to as "Inline Cells". Of course, I never use Text cells for any calculations, they are for my record keeping and documentation only, but they are indeed interspersed throughout the notebook.