Error in InputBox

[RoberSambu]

Hello,
I have a problem with an error that
sometimes occurs in a program, while most of the time it works fine.

The error Message is:

Error: HMG 3.4.4 Stable (32 bits)
Window: _InputBox is not active. Program terminated
Called from _RELEASEWINDOW(3880)
Called from DOMETHOD(9020)
Called from (b)INPUTBOX(5393)
Called from _DOCONTROLEVENTPROCEDURE(6056)
Called from EVENTS(2251)
Called from DOEVENTS(0)
Called from _SHOWWINDOW(4003)
Called from _ACTIVATEWINDOW(5688)
Called from INPUTBOX(5418)
Called from ENTRO_X1(1206)
Called from (b)GRAFI2(480)
Called from _DOCONTROLEVENTPROCEDURE(6056)
Called from EVENTS(1801)
Called from DOMESSAGELOOP(0)
Called from _ACTIVATEWINDOW(5717)
Called from DOMETHOD(9003)
Called from GRAFICS_2(534)

The line of code that originates the error:

534 cDimX:= InputBox ( 'milimetros' , 'Dimension X' , str(Dim_x,5) , 2000)

this error occasionally occurs in this line of code or others that use
the InputBox function.

Any idea of how to fix it?

Thank you all
Roberto Sambuceti,
Argentina