The suggested solution did not solve my problem. Everytime I pressed Save or Apply all the values (alignment, spaces etc.) were lost. To solve this issue I changed a parameter in the TinyMCE plugin. The "Code cleanup on save" parameter was set to Always. I changed it to Never. That was it. I don't know why it was set to Always, but I guess the Joomla crew wanted it to be that way from version 1.5.14.