samimajed,
You are right. The property should be ImageGalleryPath.
You can use a full path for the ImageGalleryPath property. That should not be a problem.
I just made a test myself again. It works fine. I can't reproduce the problems...
Can you tell me your site URL and let me have a look at it?
asp.net Chat http://cutesoft.net/ASP.NET+Chat/default.aspx
Web Messenger: http://cutesoft.net/Web-Messenger/default.aspx
asp.net wysiwyg editor: http://cutesoft.net/ASP.NET+WYSIWYG+Editor/default.aspx
asp wysiwyg html editor: http://cutesoft.net/ASP
asp.net Image Gallery: http://cutesoft.net/ASP.NET+Image+Gallery/default.aspx
Live Support: http://cutesoft.net/live-support/default.aspx