I cannot emulate the fault, but maybe you should try and alter some of the command line switches.
In the properties, in mine, for example, it reads
%SystemRoot%\explorer.exe /e, /n, C:\
The e opens the window to defalt size.
the n opens a single pane window, usually the root if you have not specified anything else.
The C:\ is , in my case, my required default opening window.. This could be anything D:\ or C:\Users etc..