I have upgraded to 10.3 from Mathematica 9.0. However, in 9.0 things that ran well will not run in 10.3.
A typical example is:
Button["Import File", Import[SystemDialogInput["FileOpen", ".txt"], "List"]]
The code above runs in 9.0, but an error is generated in 10.3. I wonder whether in 10.3 the method used has changed which causes Mathematica to emit the error.
The error message is:
SystemDialogInput::nprmtv: SystemDialogInput is not currently supported within preemptive evaluations. >>