We'll definitely have a list of commonly used regexes. I dont think having a separate Troubleshooting area is a good idea as that defeats the purpose of breaking up the rest of the forum into sections.
There si already a list of frequently asked questions here
http://calibre-ebook.com/user_manual/faq.html, if peopl ehave any others they want added, feel free to post them (and their answers if possible) and I'll add them to that list.