Using Calc 7.3.7.2 when I right-click on a cell, the “copy” option no longer appears. This worked a couple of hours ago then suddenly changed for no apparent reason.
Now the menu contains weird items like “word is Sardinian” but not Copy, Paste, etc. What I actually need is “Paste Special” but it’s not there. This appears to affect some cells but not others. The one I want to copy has a validation list, but that never stopped it from working before.
When you right-click on a work marked as a grammar error, the grammar checked context menu is shown. Either disable automatic spell check, or correct the mistakes, or set the cells’ language properly, so that the check wouldn’t give false positives.
OK, that’s a work-around, but I don’t understand why it happened in the first place. This is a spreadsheet I’ve been using for years without this issue.
In such cases, an accurate diagnosis is difficult. 
Maybe you (accidentally) typed Shift+F7, which is equivalent to Menu / Tools / Automatic Spell Checking…
…Or right-click on the partial area of the cell where there is not text.