Hey Thao, thanks for the post... did you ever get this resolved? I seem to be having the same issue.
We have WPF maps embedded in another application and multiple maps can be opened. Most the time everything is fine, but once in awhile the application will just hang for one to two minutes. It seems that it is hanging at a simple QueryTask (which is called on each map load) which usually returns in a split second. It is hard to reproduce, so haven�??t pinpointed it exactly, but it seems to always be when a second map has been up or loading.
Both maps are calling a static method which creates a new QueryTask and then executes it inline (because I need the method to return results). I don't see any errors in the AGS logs either. I haven�??t noticed this error until recently upgrading from the 2.2 API to the 2.4, but I have changed other code that might just be exposing this error more now.
Thanks for any info!