First of all, thanks for your response
This problem seems to occur with all pdf files that I try to upload (tested 5 of them so far). There is absolutely nothing in the server log ...
I tested connecting to RE from my computer and directly from the server, both have the same problem.
I'm using ReaderExtensions V8.0 by the way.
Flash Player 10 broke the Reader Extensions sample application included with LiveCycle ES 8.0.1, and 8.2.1. When you use it, it will essentially hang. The workaround is to revert back to Flash Player 9 on those machines you use as LiveCycle clients.
This problem has been fixed in LC 8.2.1 SP3 as well as in ES2.