Quad Capture (Roland UA-55) +DXi = freeze

I have found a strange bug, and I think it is specific to Reaper, at leat partially.
I am using Reaper 4.22 (rev c07d16).
When using DXi instrument, at least Cakewalk TTS-1 and AlienWare Revalver (that I got with Sonar Producer 4), Reaper freezes.
And even more, the Quad Capture ASIO becomes then unavailable, even to other DAW (Sonar Producer 4 and Sonar X1 LE).
Another symptom: if I "kill" Reaper, it stays present in the processes list and all I can do is usually to reboot the computer, in order to close Reaper and to be able to use UA-55 ASIO again. Even logging off does not always kill reaper (in Windows 7, I then get a ghost session with only CRSS.exe and Reaper.exe).

This does not seem to happen with Sonar X1 LE nor with Sonar Producer 4: DXi can be used just fine (but I can say that I have done a lot of testing).

Test environment:
Windows 32bits. I used Windows XP sp3 on an ACER E560 HE79 and Windows 7 on an HP Compaq Elite 8000 SFF. Same result.
I used UA-55 drivers v1.0.1 (the ones on the CD) and v1.50 (from roland.com site): Same result.
I tried the various Reaper combination for ASIO drivers (Pre-zero... Ignore): Same result.

I usually configure Quad-Capture ASIO for 48000kHz and a block size of 128.


I am a professional of computer development (I used to develop WDM kernel drivers, at an "intermediate level", and some applications involving a lot of interactions with system layers and Windows APIs) so I can do things such as creating dump files of the frozen Reaper if that could be useful, run diag tools, alpha/beta versions, import Reapers symbols and dumpa a stack trace etc., use Windows debugger, if I am told what to do.

Maybe not a very high priority issue (who uses DXi these days? Well TTS-1 was great and there is no real VST equivalent ), but still worth reporting