Hi there,
Thanks for using Hikashop, it's always good to hear people trying our system and appreciating it, I hope you won't be disappointed!
About your issue, if it works with the beez5 theme, it means it definitely has something to do with the CSS. First of all though, I would suggest to update to the very last version of Hikashop (2.3.0 that you can download on our site). There have been a lot of improvement and it might help a bit. Second, did you take a look at the code where the label should be? If you don't have a url, you can post here a screen shot with the inspector panel activated so we can see if there is any css that shouldn't be there.