Your operating system?
Selected code page on the top of ASCII chart?
It's really 117 build? Can you add screenshot?
Does anybode else has a similar problem?

Yes, it's 117. On Windows 10, no system theme modifications. Codepage doesn't
matter and while trying different codepages I also got this randomly:

Exception description:


Invalid code page.

Exception class: EEncodingError
Exception address: 00434D9D
--------------------------------------------------------------------------------
--------------------
Stack list, generated 10/3/2017 16:18:37
[00434D98] System.SysUtils.TMBCSEncoding.Create + $58
[004090D7] System.TObject.NewInstance + $13
[004098DB] System.@ClassCreate + $7
[00434D1C] System.SysUtils.TMBCSEncoding.Create + $24
[00434A33] System.SysUtils.TEncoding.GetEncoding + $57
[008A0C67] uASCII.TfASCII.FillAsciiChart (Line 354, "uAscii.pas" + 2) + $2
[008A172C] uASCII.TfASCII.cbEncodingChange (Line 522, "uAscii.pas" + 0) + $0
[00542184] Vcl.StdCtrls.TCustomCombo.Change + $1C
[005416EC] Vcl.StdCtrls.TCustomComboBox.Change + $50
[0054234F] Vcl.StdCtrls.TCustomCombo.Select + $23
[00542102] Vcl.StdCtrls.TCustomCombo.CNCommand + $116
[0064A265] Vcl.Controls.TControl.WndProc + $2BD
[0064EEB6] Vcl.Controls.TWinControl.DefaultHandler + $E6
[0064F74F] Vcl.Controls.TWinControl.WMPaint + $3B
[0064EDA5] Vcl.Controls.TWinControl.WndProc + $5E9
[004D4950]
System.Classes.{System.Generics.Collections}TDictionary<System.Integer,System.Cl
asses.IInterfaceList>.TryGetValue + $4C
[004CFBC1] System.Classes.TObservers.IsObserving + $2D
[004CFC3C] System.Classes.TObservers.IsObserving + $A8
[00541FDF] Vcl.StdCtrls.TCustomCombo.WndProc + $1B3
[005438F1] Vcl.StdCtrls.TCustomComboBox.WndProc + $155
[00649EA0] Vcl.Controls.TControl.Perform + $24
[0064EF0B] Vcl.Controls.DoControlMsg + $23
[0064F993] Vcl.Controls.TWinControl.WMCommand + $B
[0064A265] Vcl.Controls.TControl.WndProc + $2BD
[0064EDA5] Vcl.Controls.TWinControl.WndProc + $5E9
[004D4950]
System.Classes.{System.Generics.Collections}TDictionary<System.Integer,System.Cl
asses.IInterfaceList>.TryGetValue + $4C
[004CFBC1] System.Classes.TObservers.IsObserving + $2D
[004CFC3C] System.Classes.TObservers.IsObserving + $A8
[00541FDF] Vcl.StdCtrls.TCustomCombo.WndProc + $1B3
[0040CCF8] System.@FinalizeArray + $E4
[0040A134] System.TMonitor.TryEnter + $28
[0064EDA5] Vcl.Controls.TWinControl.WndProc + $5E9
[0040A134] System.TMonitor.TryEnter + $28
[00409CBC] System.TMonitor.Enter + $10
[0064EDA5] Vcl.Controls.TWinControl.WndProc + $5E9
[00409E9B] System.TMonitor.Exit + $F
[005173D7] Vcl.Graphics.FreeMemoryContexts + $9B
[0064E3C4] Vcl.Controls.TWinControl.MainWndProc + $2C
[0064E3D9] Vcl.Controls.TWinControl.MainWndProc + $41
[0064E3C4] Vcl.Controls.TWinControl.MainWndProc + $2C
[004CE4F4] System.Classes.StdWndProc + $14
[0064EEB6] Vcl.Controls.TWinControl.DefaultHandler + $E6
[0064F9A2] Vcl.Controls.TWinControl.WMCommand + $1A
[0064A265] Vcl.Controls.TControl.WndProc + $2BD
[0064EDA5] Vcl.Controls.TWinControl.WndProc + $5E9
[004D4950]
System.Classes.{System.Generics.Collections}TDictionary<System.Integer,System.Cl
asses.IInterfaceList>.TryGetValue + $4C
[004CFBC1] System.Classes.TObservers.IsObserving + $2D
[004CFC3C] System.Classes.TObservers.IsObserving + $A8
[00541FDF] Vcl.StdCtrls.TCustomCombo.WndProc + $1B3
[005438F1] Vcl.StdCtrls.TCustomComboBox.WndProc + $155
[0064E3C4] Vcl.Controls.TWinControl.MainWndProc + $2C
[004CE4F4] System.Classes.StdWndProc + $14
[0062199D] Vcl.Forms.TApplication.CancelHint + $11
[0062062F] Vcl.Forms.TApplication.ProcessMessage + $F3
[00620672] Vcl.Forms.TApplication.HandleMessage + $A
[006209A5] Vcl.Forms.TApplication.Run + $C9
[00991921] PSPad.PSPad (Line 69, "PSPad.dpr" + 35) + $7
--------------------------------------------------------------------------------
--------------------
Program  : C:\Program Files (x86)\PSPad\PSPad.exe  5.0.0 (117)
System   : Windows 10 Professional x64, Version: 10.0, Build: 0, 
Processor: Intel,         Intel(R) Core(TM) i5-3470 CPU @ 3.20GHz, 3200 MHz MMX
Display  : 1280x1024 pixels, 32 bpp
--------------------------------------------------------------------------------
--------------------
Active Controls Hierarchy:
TComboBox "cbEncoding"
TTabSheet "tsAscii"
TPageControl "PageControl"
TfASCII "fASCII"
TPanel "pageDock"
TfPSPad "fPSPad"
--------------------------------------------------------------------------------
--------------------


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