Well, in my case I could actually think it had to do something with my Cache and Cookies of the browser. I usually log on and off of accounts on the fly to buy stuff and that issue has never occurred to me before, without clearing out the cache and cookies.
I haven't re-tried buying stuff now, I will wait for the answer from the ticket service. It's quite frustrating, as I actually wanted most of those items so I can work on some textures and build a personal character.
Though that case indeed is weird, I seriously believe there is something wrong with the system. Though in my case I never got the purchase email to the email attached to the right account, but got the purchase email to the account the items landed on. Nothing sent as a gift.
I just filed a ticket, so I would say you should do the same, so Linden Labs is going to be aware about this issue. It's absolutely weird indeed, I seriously don't understand what is going on there,