Could not find class error when trying to upload a video to YouTube using the gdata API

I am currently writing part of an Android application to upload a video to YouTube using the Google Data API. I have the latest version of the API from Google Code, and I have basically copied the example from their Developer's Guide for the time being. Everything compiles with no warnings or errors, and the app runs fine. But when I call service.insert(...) I get the following stack trace: ``` ERROR/dalvikvm(19489): Could not find class 'com.google.gdata.data.media.MediaBodyPart$MediaSourceDataHandler', referenced from method com.google.gdata.data.media.MediaBodyPart.initMediaDataHandler ERROR/dalvikvm(19489): Could not find class 'javax.activation.DataHandler', referenced from method com.google.gdata.data.media.MediaBodyPart.initMediaDataHandler ERROR/dalvikvm(19489): Could not find class 'javax.mail.internet.MimeBodyPart$MimePartDataHandler', referenced from method javax.mail.internet.MimeBodyPart.writeTo ERROR/dalvikvm(19489): Could not find class 'javax.activation.DataHandler', referenced from method javax.mail.internet.MimeBodyPart.attachFile ERROR/dalvikvm(19489): Could not find class 'javax.mail.internet.MimeBodyPart$MimePartDataHandler', referenced from method javax.mail.internet.MimeBodyPart.getDataHandler ERROR/dalvikvm(19489): Could not find class 'javax.activation.DataHandler', referenced from method javax.mail.internet.MimeBodyPart.setContent ERROR/dalvikvm(19489): Could not find class 'javax.activation.DataHandler', referenced from method javax.mail.internet.MimeBodyPart.setContent ERROR/dalvikvm(19489): Could not find class 'javax.activation.DataHandler', referenced from method javax.mail.internet.MimeBodyPart.updateHeaders ``` with a NoClassDefFoundError. I have all the dependencies for the gdata API linked to my project in Eclipse (the two included in the deps directory of the API, and also javamail, activation and servlet-api), and I have tried adding all the jar files to the classpath in Eclipse. I have looked through the relevant jars and all the classes it claims it can't find are definitely there. If anyone could help in any way - any ideas at this stage would be greatly appreciated. Thanks