I would say you're nearly there in fact Colin. You have all the right stuff, you just need to set it up slightly differently.
You have 3 lights, a light box and a camera. A tripod or some other method of holding the camera other than by hand would be useful too by the way, if you don't already have one.
Your main problem I think is the positioning of your lighting though.
There are other ways of doing it, but perceived wisdom for a three light system is that one of the light shines down from above, often slightly behind the subject. The tent will diffuse it, which as Brad says, will help to eliminate glare. The other two, in general terms should shine in at the floor level of the tent, or near to it, from the front corners of the tent, or maybe from the sides - a bit of experimenting will help you work out which is best, and depending on the subject you may find that the two are not necessarily positioned symmetrically.
You may already be doing that, but the thing is that you consistently have a harsh shadow created by the top light, which implies that the two side lights are either not strong enough or are too far away.
The purpose of the lighting positions is to illuminate the front, sides and top of the subject AND the area behind it, thereby softening the shadow from the one above. You need to know though, that a light 1 foot away will cast twice the light of one that is 2 feet away. If you double the distance, you halve the light, or conversely, if you halve the distance you double the light. Therefore bring the side lights nearer, or move the top light further away until by either method you get a balance. In fact you may find that a combination may be helpful, as increasing the top distance a little may help you reduce the high spots you are getting.
White balance has been mentioned already, which is also important, as has the ability to tweak in some sort of photo editor, which is also a benefit, but your main issue, as I see it, is the position and distance of your lights.
