S7 200 Microwin IEC1131 error

Hi All
I am trying to open a .mwp file with Microwin Ver4.0 and get the following error
"Cannot Open IEC 1131 Project In curent Mode"
Any Ideas what the problem could be? The original project was written with Ver 4.0.

Thanks

you may need to change the programming mode of microwin to iec mode instead of simatic
this is under tools options general then close and restart microwin