Alright, I think now I figure out that was going on:
I generate the missing key manually:
So I went to the folder:
and execute the keytool.exe with the parameters shown in the line that was showing me the error:
keytool.exe -genkey -alias rhomobile.keystore -keyalg RSA -validity 20000 -keystore C:/Users/cmn478/.rhomobile/keystore -storepass 81719ef3a881469d96debda3112854eb -keypass 81719ef3a881469d96debda3112854eb
I guess those -storepass and -keypass parameters are particularly for each computer.