exception: Unable to cast object of type ‘System.Windows.Forms.SplitContainer’ to type ‘System.ComponentModel.ISupportInitialize’.
When downgrading a client winform app from Dotnet4 to Dotnet3.5 one might get
Unable to cast object of type 'System.Windows.Forms.SplitContainer' to type 'System.ComponentModel.ISupportInitialize'.
The solution in my case was to just comment out the offending row (BeginInit) and its (EndInit) counterpart.
There is an early bug report on the subject but the error seems to linger.