I keep using your prog, both on Win and Linux boxes, and I've come into a strange behaviour. Focus area is renaming with regexps, and specifically capitalization with a character class.
My point is to capitalize roman numerals inside (rather long) filenames, and I've come to a quite simple regex like:
\b(+)\. (or: beginning of word, class of 3 chars comprising roman numerals, one or more times, followed by a period)
inserted into a "modification" action. In case of match, uppercase matching characters.
Result is a loss of preview of names after the first (successful) change, high CPU consumption, continuous hourglass in Windows (and equivalent in Linux).
The issue appears to be the character class: if - instead of having a single regexp, I go for the lengthy way (separately change each roman numeral - \bi.\b, then \bii.\b, etc) program works like a charm, even if this way i've more than 90 distinct operations for each set of filenames.
Suggestions or workarounds are welcome - in case I can provide some real-life examples, and eventually promote this RFI to a bug.
Thanks again for all the good work