are you trying to install new EPM 126.96.36.199 product with the same user who had performed maintenance from epm 122 to 123 ?
make sure you install new EPM 188.8.131.52 product with the same user.
yes, I'm sure.
Is there any possiblity that user rights/provision got changed after applying maintenance?
Just a thought..
Look at the root of your middleware home and you wil see a text file listing all products installed with the version and you will see that there is some products version that were not updated on the text file (EPM in place upgrade is faulty...). Change manually the version in this text file and the EPM install tool will let you install FDM