There is a bug somewhere in LibreOffice (also in OpenOffice) that makes it freeze on startup when the LanguageTool ([url removed, login to view]) extension is installed. Some analysis can be found here (make sure to read all the comments):
[url removed, login to view];aid=3153545&group_id=110216&atid=655717
The task is to install LibreOffice and LanguageTool to reproduce the bug (note that it's only a bug if it freezes for more than about 4 seconds), find the cause of the bug and write a clean and documented patch for LibreOffice to fix the issue. You will need to compile LibreOffice for that, as we are quite sure that the bug is there and not in LanguageTool.
You will need to test your solution carefully as the bug's reproducibility depends on factors that haven't been completely understood. That means you really have to make sure that it's your change that fixes the problem, not pure luck.