Could the issue be related to cgminer not supporting cpu mining anymore (I believe guiminer is a front end for cgminer)? I think it would be easiest to run it the same way tmu does, using pooler to mine with the cpu instead.
No, you've understand it wrong. GUIMINER for GPU uses cgminer.exe, but for CPU setup it runs "guiminer-scrypt_win32_binaries_v0.04\reaper-bb\reaper.exe". I've post settings for cgminer just to show how this stupid GUIMINER made wrong settings for GPU also (but I've fixed cgminer for GPU with manual changes, with help at IRC (chat)).
OK, I will try this "pooler-cpuminer" for CPU. I am new in all this, this is my first day, so I didn't know that there are more applications
.