Access violation at address 00621407 while adding new column

When I was adding new columns to a table I got the following error a few times when navigating between cells (Name, Datatype and Length/Set) with TAB:

date/time : 2010-10-22, 17:42:08, 781ms
computer name : xxx
user name : xxx
registered owner : xxx
operating system : Windows Vista Tablet PC Service Pack 2 build 6002
system language : Polish
system up time : 44 minutes 1 second
program up time : 49 seconds
processors : 2x Intel(R) Core(TM)2 Duo CPU E8235 @ 2.80GHz
physical memory : 889/2028 MB (free/total)
free disk space : (C:) 16,94 GB
display mode : 1920x1200, 32 bit
process id : $15e4
allocated memory : 55,17 MB
executable : heidisql.exe
exec. date/time : 2010-10-22 17:07
version : 5.1.0.3568
compiled with : Delphi 2010
madExcept version : 3.0k
callstack crc : $bb969e7e, $556f25cc, $556f25cc
exception number : 1
exception class : EAccessViolation
exception message : Access violation at address 00621407 in module 'heidisql.exe'. Write of address 0063007D.

main thread ($1530):
00621407 heidisql.exe VirtualTrees TBaseVirtualTree.InitNode
00628a11 heidisql.exe VirtualTrees TBaseVirtualTree.GetNextSelected
006279b0 heidisql.exe VirtualTrees TBaseVirtualTree.GetFirstSelected
00617e85 heidisql.exe VirtualTrees TBaseVirtualTree.WMKeyDown
006776db heidisql.exe grideditlinks 324 +8 TBaseGridEditorLink.TempWindowProc
0053a784 heidisql.exe Controls TControl.Perform
00541896 heidisql.exe Controls TWinControl.CNKeyDown
0053ab60 heidisql.exe Controls TControl.WndProc
77385dab ntdll.dll KiUserCallbackDispatcher
0053a784 heidisql.exe Controls TControl.Perform
0053ab60 heidisql.exe Controls TControl.WndProc
0053f428 heidisql.exe Controls TWinControl.WndProc
00625288 heidisql.exe VirtualTrees TBaseVirtualTree.WndProc
006776db heidisql.exe grideditlinks 324 +8 TBaseGridEditorLink.TempWindowProc
0053eac8 heidisql.exe Controls TWinControl.MainWndProc
0049a524 heidisql.exe Classes StdWndProc
75d2d0e7 kernel32.dll BaseThreadInitThunk

I can reproduce it sometimes but it doesn't happen always. Heidi seems to continue functioning after pressing 'continue'.

This is what issue #1677 reported. Very mysterious. Tried to fix that for the third time, without any luck. Does only occur in the table editors column list - nowhere else.

Recently I had a similar one on build 3579:

date/time : 2010-11-05, 18:24:03, 781ms
computer name : xxx
user name : xxx
registered owner : xxx
operating system : Windows Vista Tablet PC Service Pack 2 build 6002
system language : Polish
system up time : 2 hours 16 minutes
program up time : 46 minutes 49 seconds
processors : 2x Intel(R) Core(TM)2 Duo CPU E8235 @ 2.80GHz
physical memory : 848/2028 MB (free/total)
free disk space : (C:) 13,44 GB
display mode : 1920x1200, 32 bit
process id : $152c
allocated memory : 79,71 MB
executable : heidisql.exe
exec. date/time : 2010-11-04 17:01
version : 5.1.0.3579
compiled with : Delphi 2010
madExcept version : 3.0k
callstack crc : $8554e145, $bb41deaa, $bb41deaa
exception number : 3
exception class : EAccessViolation
exception message : Access violation at address 00405748 in module 'heidisql.exe'. Read of address 00000010.

main thread ($1510):
00405748 heidisql.exe System 548 +0 @IsClass
0055f10b heidisql.exe Forms GetRealParentForm
0055f140 heidisql.exe Forms GetParentForm
00543619 heidisql.exe Controls TWinControl.UpdateUIState
00540e02 heidisql.exe Controls TWinControl.WMKeyDown
0053ab60 heidisql.exe Controls TControl.WndProc
0053f428 heidisql.exe Controls TWinControl.WndProc
006776df heidisql.exe grideditlinks 324 +8 TBaseGridEditorLink.TempWindowProc
0053eac8 heidisql.exe Controls TWinControl.MainWndProc
0049a524 heidisql.exe Classes StdWndProc
77990226 USER32.dll DispatchMessageW
0056b229 heidisql.exe Forms TApplication.ProcessMessage
0056b26e heidisql.exe Forms TApplication.HandleMessage
0056b599 heidisql.exe Forms TApplication.Run
007a7742 heidisql.exe heidisql 66 +15 initialization
7642d0e7 kernel32.dll BaseThreadInitThunk

This error kept appearing consistently when tabbing through column properties - until I restarted, then it disappeared. I don't know if these bug reports tell you anything useful - hopefully you will be able to solve the mystery.

See the call to

TBaseGridEditorLink.TempWindowProc

at least both AVs have the same cause. If I only knew how to fix that. Really mysterious stuff here.