We're working on a new version of the Pivotal Tracker developer API, with a long list of improvements. The release of this is a few months away, but to prepare for it, we're removing the old version (V2) of the API. This change (removal of V2) is tentatively planned for January 27, 2012, just over three weeks from today.
If you're using the API, please make sure that you're using the current version (V3), as requests to V2 will no longer work.
To see which version you're using, look at the URLs of the requests you're sending. If you see "v2" in the path, for example /services/v2/projects, you're using the old version, and will need to upgrade to the current API version.
If you have any questions, or could use help figuring out how to make your code work with the V3 version of the API, please send an email to tracker@pivotallabs.com.
We've been using the API with great success for a few months, and I'm eagerly anticipating the new version. Are there any plans to allow updates to member roles (editing permissions) in the next release?