This statement is at line 457 in the Barcore.cpp file.
The assertion occurs in the preceding code if the lpszText member of the TOOLTIP structure is an identifier of a string resource. In this case, the code is trying to dereference a pointer; however, *pTTTA->lpszText is "pointing" to a value instead of a valid memory location.
Copy the address of the buffer that contains the text to the lpszText TOOLTIP member. If the text to appear as tool tip text is stored as a string resource, use the LoadString function to load the string from the string table into a buffer and assign that buffer to the lpszText TOOLTIP member.
Microsoft has confirmed that this is a bug in the Microsoft products that are listed at the beginning of this article.
This bug was corrected in Visual Studio 6.0 Service Pack 3. For more information about Visual Studio service packs, please see the following articles in the Microsoft Knowledge Base:
194022 INFO: Visual Studio 6.0 Service Packs, What, Where, Why
194295 HOWTO: Tell That Visual Studio 6.0 Service Packs Are Installed
This bug was introduced in Visual C++ version 6.0 with the reimplementation of the CControlBar::WindowProc() function.
See the document titled "The TOOLTIPTEXT Structure" in the online documentation included with Visual C++ 6.0 for more information about how to initialize the members of the TOOLTIPTEXT structure.