Os change doesn't work

Hi there,
I own the Mpc1000Bk with jj os1 4.99l on it. today i changed the os back to V.1.07 to try out the jessiah glitch. The os installation worked well. now i want change back to jjos1 4.99l, but if i hit the load screen and pick out the os file it won't load it... seems like the do it button F6 doesn't work. but if i want to load a sample or program F6 works perfectly!
What the hell is wrong? Need Help

(There's a whole section of this site devoted to JJOS, this thread should be there.)

Did you download the 4.99l file yourself, or was it there already?

sounds like the file might not be valid (e.g. if it was a saved HTML page not the file itself)

no, its the right file. I bought the mpc secondhand with jjos4.99 on it. later i updated to 4.99l and now to akais 1.07
they are the same .bin files and they worked before