In my many years of training and consulting, I have met just about every kind of person except one - the intentional saboteur. Given how many things, especially on remote teams, go kablooey on a regular basis this seems statistically unlikely.
Whenever I meet the person who's being blamed for making something go wrong, I have never had one yet say, "yes, I intentionally missed that deadline just to make so-and-so's life a living hell". It's just not the primary reason for the behavior (although an occasionally satisfying benefit).
No, it takes a special kind of sociopath to admit to intentionally making something go wrong for purely malicious reasons. And , let's face it, some things go so spectacularly wrong they couldn't have been planned. The person in question is just not that capable. (That's why I don't believe in most government conspiracy theories - it's the government).
This leaves one other possibility that is much more likely: The problem is not so much that they CHOSE to blow off the deadline (necessarily) it's that they CHOSE to do something else instead.
Assuming the teammate is a rational human being, this makes a lot more sense. But why would they choose to do something other than help your project to be successful? Well that's a pretty simple question to answer. Basically, people choose to do (or not do) something based on very simple criteria.
There is an obvious reward for doing something else: remember that on a virtual or project team, you often don't have direct line-of-sight responsibility for the person's work. They work for someone else. Odds are your project isn't even on their performance review, but something their boss wants them to do is. They might get your undying gratitude for their hard work but it doesn't get them a "surpasses expectation" at salary review time.
So what's competing for your teammate's time and attention? Are you rewarding and recognizing team contributions (especially in front of other teammates who might learn how terrific they are and quit treating them like that idiot in the other office)?
The other thing they were doing was easier: let's face it, you don't work where they do so when that person in the next cubicle asks them for help on something, it becomes more important than what they were doing for your project. Just doing the thing and shutting them up is often an important part of office dynamics (and some marriages, but I digress).
Also, doing things the way they're used to doing them is easier than learning a new system - it's certainly easier than trying to get Joanne in Boston to get you the data you need or to learn that share filing system you're so insistent they use. Are you offering the training and support they need to learn the job? Are you giving them the tools they need? If not, why are you surprised they're doing something else instead?
They like the other person better: All things being equal, someone will work harder and put more effort into a task for someone they like, respect or want to help more than someone they simply report to.
The human relationships people form are crucial to deciding where they'll put their efforts. If they see other people all day, occasionally go to the pub with them and get told by their cubemates how adorable their children are, while you are all business and demands, are you really surprised they'd help someone else before you?
Ignoring the human dynamic on a virtual team is easy to do, but the costs are surprisingly high. Trust me, it's easier to take a deep breath, suck it up and ask how their kids' ballet lesson went. Caring about the answer is actually optional.
Without understanding why people choose to do one thing over another, their behavior will consistently surprise and irritate you. Understanding it will still irritate you, but it will be much less of a surprise. And some days that's all you can ask for.