I have the same problem ... and yes went to the above topic .. still no direct answer...
I have one sub directory of the above main problem domain but it does not have this problem. It can upgrade plugins automatically.
i checked the permission, all the same.. so whats the difference between the main directory and the sub directory??? Sub directory is my test wordpress site.
can anyone help me. thanks.
for info, if the server is the problem, why the sub can auto upgrade??? thats the question now too.. so confusing.. pls anyone.. help me.