Hi, and thanks for your reply.
Apart from the Joomla project extensions that came with Joomla, I have: AllVideos (by JoomlaWorks), Articles - FJ Related Plus, Button - NoNumber Articles Anywhere, Codeboxr Flash SWF, Content - JosDewPlayer, Content Pdf Embed, EasyTagCloud, Editor (CodeMirror, JCE, and TinyMCE), Multimedia Box (Youjoomla), Simple Image Gallery (by JoomlaWorks), TopCloud, fwTagsJoomulus.
I use "protostar" as template.
Are there any known incompatibility issues with any of these?