This issue has been written up under the following hot topic article
Integration Manager for Microsoft Dynamics GP 2010 is Unresponsive at the Beginning or End of an Integration [link broken as hot topic has been retired]
According to a Microsoft representative with the Escalation Engineering team:
Our development team has identified the issue to be the result of a change in .Net Framework 3.5. At this point our development team is working on creating a new Integration Manager build which will then undergo testing to verify the build and that the issue has been resolved. As soon as we have a new IM build that resolves this issue, we will post the install on CustomerSource/PartnerSource so you can download the update and begin updating your IM installations to correct this issue.
Microsoft .NET Framework 3.5 was released in 2,007 and has since undergone a Service Pack 1 release in November of 2,008, and some security fixes just in July of this year.
Other releases of Integration Manager appear not to be affected by this as they use earlier versions of the .NET Framework.
Until next post!
Mariano Gomez, MVP
Updated 04/05/2012 - Hot topic retired as issue has been corrected. URL broken.