From: Tortuka on
i faced the same problem,

i think it happens, if you try to access the 'videoinput' variable from more than one .m file

try to access the 'videoinput' with only one file at a time, if by mistake you happen to open two different .m files, than just simply restart MATLAB, and make sure, you use 'videoinput' from sigle .m file

this way, it solved my problem, i hope it does your...

best of luck