TYPE_E_CANTLOADLIBRARY when using a COM object on a separate thread on Windows 2003 x64 only

Question

Hi all,

I have a Windows Forms app (compiled as x86) accessing a COM object. It gives me the following error, only on Windows 2003 x64, when the code is run on a separate thread:

Exception during creation of IDoc:Unable to cast COM object of type 'PTISG.COM.TeklogixQueue.QueueClass' to interface type 'PTISG.COM.TeklogixQueue._Queue'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{3CBD7297-27D8-11D6-B75D-00902761DFA4}' failed due to the following error: Error loading type library/DLL. (Exception from HRESULT: 0x80029C4A (TYPE_E_CANTLOADLIBRARY))

And the code looks like this:

Private Sub Button3_Click(...)
    If _separateThreadCheckBox.Checked Then
        Dim t As Thread
        t = New Thread(AddressOf Me.CreateQueue)
        t.Start()
    Else
        Me.CreateQueue()
    End If
End Sub

And CreateQueue() looks something like this:

Dim q As New TeklogixQueue.Queue q.Object = .... 'Has to use the object

I've tried the same code on different OS and here's the result:

• Windows 7 x64. Works.
• Windows 2008 x64. Works.
• Windows 2003 R2 Server Standard x64. Fails.

If I don't execute the code on a separate thread, then it works on all platforms.

I've used ProcessMonitor to capture the registry reads for that interface id, and here's one difference between Windows 2003 vs. Windows 7:

Windows 2003:

"1:09:13.2616131 PM","IDocSend.exe","2704","RegOpenKey","HKCU\Software\Classes\Wow6432Node\Interface{3CBD7297-27D8-11D6-B75D-00902761DFA4}","NAME NOT FOUND",""

"1:09:13.2616360 PM","IDocSend.exe","2704","RegOpenKey","HKCR\Wow6432Node\Interface{3CBD7297-27D8-11D6-B75D-00902761DFA4}","SUCCESS",""

"1:09:13.2617100 PM","IDocSend.exe","2704","RegQueryKey","HKCR\Wow6432Node\Interface{3CBD7297-27D8-11D6-B75D-00902761DFA4}","SUCCESS","Query: Name"

Windows 7:

"1:10:01.6212010 PM","IDocSend.exe","4548","RegOpenKey","HKCU\Software\Classes\Wow6432Node\Interface{3CBD7297-27D8-11D6-B75D-00902761DFA4}","NAME NOT FOUND","Desired Access: Read","32-bit"

"1:10:01.6212518 PM","IDocSend.exe","4548","RegOpenKey","HKCR\Wow6432Node\Interface{3CBD7297-27D8-11D6-B75D-00902761DFA4}","SUCCESS","Desired Access: Read","32-bit"

"1:10:01.6212927 PM","IDocSend.exe","4548","RegSetInfoKey","HKCR\Wow6432Node\Interface{3CBD7297-27D8-11D6-B75D-00902761DFA4}","SUCCESS","KeySetInformationClass: KeySetHandleTagsInformation, Length: 0","32-bit"

"1:10:01.6213324 PM","IDocSend.exe","4548","RegQueryKey","HKCR\Wow6432Node\Interface{3CBD7297-27D8-11D6-B75D-00902761DFA4}","SUCCESS","Query: Name","32-bit"

Note on Windows 7, there's an extra "RegSetInfoKey" call.

Also, if I don't run on a separate thread, there's nothing captured in ProcessMonitor. Dunno why.

Anyone has an idea why this fails on a separate thread?

Thanks, Harold