Im a lev 10 night elf hunter, i just started the quest that allows me to get pets. I just taimed the spider, and then returned to complete the quest. I was then assigned the task of taiming a knight saber stalker. My spider died, and now whenever i try to taim a night saber the taiming staff button doesnt work. I cant even taim another spider.

You have a button to revive your pet, and you can dismiss it from there. You may be able to dismiss it while it's dead too, but I can't remember. Check your hunter skill buttons, they should be in there.

I'm pretty sure the problem is you're using the spider taming rod. You get a new rod for each pet you tame in the hunter quest. The reason you can't get another spider is I believe they only have 1 charge each.

Revive the spider, right click it's name, click abandon, now you can tame