Thanks for following up on this and posting the solution. I had exactly the same problem with a C# application, compiled in Visual Studio 2008 on 64-bit Windows 7 RTM. I had to do two things to get my project to work: (1) As you point out, change the target platform from "Any" to "x86". (2) Instead of creating the AxTws control dynamically, I have to put it directly in my windows form (i.e. put it in the toolbox, then drag it onto my form). I can't remember where I saw this discussion, but apparently if you create the control dynamically, initialization may not be carried out properly. That's why I have to do Step #2 as well.
Just want to chime in: I've been testing on 64 bit Ubuntu with 64 bit JVM for weeks now and it's running without any problems. Just upgraded to the latest TWS and API and so far no problems. Just to clarify: I've been on 64 bit ubuntu for 18 months and tested against TWS many times. Recently I've begun preparing to go live, and have let the paper account trade on full auto just to see. That's what's going well.
Does anybody know where I can download the Tws.ocx? I am writing the API in C# and according to this tutorial, I am supposed to place this activeX control on the form but this control is nowhere to be found in the API folders in the latest TWS API version 9.7.2 or 9.7.3. so I can't even register it to be used in the project. Thanks.