Tying it to RDP seems pure speculation at this stage, especially if we're talking about modern versions of Windows. (RDP on Windows XP had some issues, although mainly to do with CPU usage from the clipboard components.) I use RDP extensively. For the last month I've used RDP all day, every day because I've damaged my back, can't sit down, and have to use a laptop on the floor while RDPing into my workstation. I've literally never seen this problem.
We can't fix a bug when there's no proof the bug is in Opus, and when we have nothing go on, and when only one or two people are seeing it (we don't know if both of you are seeing the same problem; lots of components can cause memory leaks and you may each have leaks from different things).
If you want us to believe there is a bug or have a chance of fixing it, you have got to use the guides and tools we pointed you to. it is the only way. There's no magic wand we can wave over the source code to magically fix something when we have no indication or where the problem is or if it is even a problem in Opus itself. We can't do anything from our end, unless you want to ship the machine to us.
No machine is really a "fresh Windows install", either. You've got a unique combination of drivers, which may cause leaks themselves. TrueCrypt installs a filesystem driver which could cause problems (although that is unlikely as we use TrueCrypt as well and would have seen it, unless it's tied to particular settings or usage).
Heck, some drivers install shell extensions (e.g. NVidia's drivers do this, and their extensions have had several bugs). Have you looked with ShellExView or are you just assuming there are none? Most machines have hundreds of shell extensions that you would not even know were there unless you looked.
Not necessarily. Opus and Explorer are not exactly the same. A shell extension may leak memory if things are done in a certain order but not if they are done in a slightly different order, for example. There have been lots of shell extension problems that affect one program and not the other, in both directions. (But things are more likely not to have problems in Explorer because that is the one and only program most people test their extensions against.)
One thing to try:
Set Preferences / Miscellaneous / Advanced: no_external_change_notify = True and see if the problem still occurs.
If that fixes it, it's possible that the file server is generating file change events faster than Opus can process them, so the events build up into a bigger and bigger queue. If the changes stop for long enough for the events to be processed then the memory will be returned, so it's not a leak, but it can still cause problems if Opus never has a chance to process the backlog of events. It's very rare but (literally) a couple of people have run into this in unusual situations, so it is worth ruling out.