If you click Edit on the BBCode, does the image path show?
If yes, then it would appear that the image can't be found. Can you link me to your forums and I'll be able to tell you whether I did something wrong here ;p
The vBSEO error is a bug in vBSEO, they don't use the correct method to determine whether it's running on vB3 or vB4.
They need to use the following code
PHP Code:
if (intval($vbulletin->versionnumber) == 3)
to check for vB3.
Please report it on the vBSEO forums and they should be able to fix it