Same problem, different details. 

1. I am using QBO desktop (not QBO in a browser, not the old QB desktop).

2. I have not made any accts inactive, at least not in the last few years. 

3. The "Something you're trying..." error message appears randomly and mostly (only?) when I am editing an already entered transaction. 

4. My workaround is to change any one of the fields (for instance the account) and then change it back. Now I can save without the error message. 

Annoying.