If the digital camera test was successful, you've got the correct devices picked in slingbox setup, and your physical remote controls are working in IR mode, the only other reasonable possibility is that the IR Blaster isn't placed in front of the sensor properly.
I had a similar headache with a Philips DVDR-3455H. Once I found the right spot, it started working but it was very finicky. I built a small reflector out of aluminum foil to help and that fixed it up. The key though was finding the right spot to start with.
If you suspect that the remote control profile is faulty, check here for a library of custom Slingbox remotes. I saw one for your R-10 on there:
I wish I could give you a more definitive answer, I imagine you've already tried moving the transmitter end around. From what you've described though, you've done everything right so far.
I suppose you could also expand your tests with a different device. Do you have an old VCR or DVD player sitting around that's on the supported device list ? That's a stretch, but if successful you could eliminate the Slingbox hardware as a possible cause.
Glad it worked for you.
Keey an eye out for alanrichey42 on the board, he's a true wizard with custom remotes. If not for him, I would have never gotten my Philips DVD/Hard Disk recorder to work.
I goofed about the R-10 in my first post, I got the models backwards. Sorry about that, I don't see one on there.
If you don't find a way to get it working, post a thread asking for custom remote help with it.