I wonder what was wrong with the skillinfo.xml that originally came with tiara.
I would always get the "client.exe has stopped working" message shortly after pleione finished loading at the login screen.
Since some others may also want to know the reason, I'll just state it.
Skillinfo.xml is essentially the list of skills in the game. You may do various edits visually, such as the well-known IsHidden="False" change, which allows for every skill to be seen (I find this rather bad, since the skills have no point, except possibly the hot-air-balloon which Playtime is always talking about). As the version progresses, they may add in more skills for future updates, so that means that skillinfo.xml must change. Now...since you have a modded skillinfo.xml which is outdated (no new skill(s)), it means that you'll get an error and Mabi will close. The solution? Use MabiUnPack and extract the newest skillinfo.xml from data\db\skill\ and then mod it, and replace the old one with this new one.