After Mavericks 10.9.2 Update, problems running Keepass/Mono
A useful troubleshooting tool for any OS X application is opensnoop which lets you see file activity on your system. If you run sudo opensnoop -v | grep mono-sgen before launching KeePass you'll be able to watch which files it is opening as it launches.

I ran this to troubleshoot another question about KeePass problems and on my system the first launch of KeePass generates a lot of activity where Mono is opening and caching the fonts on the system in ~/.cache/fontconfig. While it is doing this the application appears to be doing nothing, as the UI doesn't appear until this task is complete which takes minutes on my system. Luckily it only seems to want to do this once, as subsequent starts are about what I'd expect.

And this is only guesswork but upgrading Mono, XQuartz or KeePass or installing other fonts might prompt Mono to regenerate this cache, resulting in another one off slow application launch. Just something to be aware of.