[Q] Please Help me! topic

I've Owned many standard HTC One X phones, plus HTC Desire HD etc etc etc and never had problems flashing etc, but with my One X+ I seem to be having a major problem.

I've followed all instructions, step by step carefully, but when it comes to the last step where I go into Recovery and try to Install my custom Rom, Viper X+ 2.1.1 I get the following error message:

"Updating Partition Details...
E: unable to open zip file.
Error Flashing Zip file.
Error Flashing zip /sdcard/roms/ViperX+_2.1.1.zip'
updating partition details"

Bootloader is unlocked, supersu been flashed all sucessfuly etc, I don't understand.

Please can someone help me and tell me what i'm doing wrong?

thanks
Matt