For an hour and a half of your time, you definitely should use the oDesk team app.
I mean, even if it was for a short 10 min meeting I would still bill them as they're occupying my time and it relates to the role.
Most reasonable clients shouldn't mind, just always make sure that you discuss this at the interview stage.
I have a couple of policies in place for this kind of thing, and during my post-hire discussion with a client, it's stated up front that meetings are billed. It's a meeting. Doesn't matter that it's a virtual meeting.
I also bill my time when attending webinars that a client wants me to be part of.
I usually record all meetings, webinars and such and send the recordings to my clients. This means if the oDesk tracking DIDN'T track the time for some reason, I have proof of the events in question.
I can then add any manual time needed. (Manual time being part of my post-hire discussion with all clients, because sometimes I can't run the oDesk Tracker when doing complex tasks such as creating video training materials.)
I've yet to have a client who was un-comfortable being billed for meeting time. If a new client does not automatically give me permission to charge for manual time, they usually give it to me once trust has been extablished, because they know how buggey the oDesk Tracker is.