Are you missing tags and categories in WordPress? This unfortunately can happen if your /tmp directory is only 100MB in size as the MySQL database will not be able write any new tmp files.
To overcome this, WordPress publishers should report the problem to the server administrator where the website is hosted so that they can increase the size.
To avoid reporting the issue in the future, you may ask the server administrator to mount /tmp as a virtual filesystem so that it will use space from the main partition.