I have found out that this issue is caused by the windows
update: "Microsoft .NET Framework 4 Client Profile for Windows 7 x64-based
Systems (KB982670)"
After it was working on my second computer, installed this update, and the
options button was grayed out, and the same message. Uninstalling this
update on both computers, and both computers are able to configure gurtle
again.
I have no idea what breaks it, but it might actually be an issue in
TortoiseSVN, that it's unable to create the Interface. As I don't have
VS2010, I cannot debug tortoiseSVN myself.
So for now the workaround is to uninstall the update.
(please don't forget to fix the preprocessor define in Debug|X64, see
comment 1!)
I have KB982670 installed for a few month now and I don't have any problems
with the x64 version of Gurtle in TSVN. So I don't think it's that Windows
update that's causing the problem.
Set the WIN64 define for debug x64 builds in r238.
Maybe there is an additional relation with something, but it is the only
thing I installed & uninstalled on my second computer that broke and fixed
it.
On my primary computer I also uninstalled the .NET framework 4 extended (as
it had to be removed prior to removing the client version)
I don't have any knowledge about how COM objects interact, so I don't have
any more insight on this matter.