Just "Negative" is fine, since that's the commonly used term for this (making an image look like a film negative), however adding invert is fine.
I don't seem to have this option (though I'd suggest a space before & after the ampersand, i.e. Black & White)...
...or this one.
"An error occurred during processing." I'd also suggest "Please verify files..." instead -- just sounds better (and the word "that" is unnecessary and basically filler).
Yes, though without knowing where this is or what it does, it's hard to say if that's the best way to say it. For example, it might be better to say "Reopen latest opened tab" or "Reopen latest closed tab" or "Reopen latest active tab" etc.
While poking around looking for these, I also saw Image > Adjust > Conbright/Gammasat. Doing a search for these terms, the only relevant results I see are related to XnView, so I'm not sure if they're a term specific to this program or what, but my initial thoughts were that they mean, and therefore should say, "Brightness/Gamma."