Recently, I have worked on a project which has this strange bug, the image url in Wysiwyg is not correctly. Only administrator can see this image while guess users can not see it.
For example : the image url which is generated by Wysiwyg :
<img src="http://www.mysite.com//index.php/admin/cms_wysiwyg/directive/___directive/e3ttZWRpYSB1cmw9Ind5c2l3eWcvcmd0LXNsaWRlci1pbWcwMS5qcGcifX0/key/ceed8184f5f336aafcc307f8623aff45/" />
In that case, the problem is that Magento is generating a dynamic link with admin path in it and the result would create Magento – TinyMCE Image Uploader – Image incorrect URL . The solution is to change just one setting in admin :
System -> Configuration -> General -> Content Management -> Use Static URLs for Media Content in WYSIWYG for Catalog to Yes
I found that this setting is checked in
/app/code/core/Mage/Cms/Helper/WYSIWYG/Images.php on line 185 ( in Magento 126.96.36.199 ) and depending on that either static or dynamic links are generated.