Clearly let me show the conditional here in showproduct which will show you where i am coming from and allows the post a review link to be shown. You have to have one of these things set to off that I see.
Code:
Content visible to verified customers only.
Therefore there can only be one of two things wrong here. You either have usergroup permissions set that they can not post which is the $userreview variable or you have allow reviews turned off in admin options which is the $Global variable. Both have to be enabled to allow reviews.
What usergroup do you show user Omegatron in? I should be in group 2
If this was the case I should also have mod access according to your picture of the usergroups which I do not so something else is seriously wrong. I suggest before anything you reupload all the files especially if this was an upgrade. I run vbulletin 3 on my site so there are no permissions issues reported or none that I see.