Windows Update killed my ABCpdf

An application I develop (dev environment: Win7 Pro, IE9, ASP.Net 3.5) suddenly showed problems running on Windows Server 2008: the web application could not create PDF documents anymore, and

• The browser only displayed a “Service Unavailable” message

• The browser user was automatically logged out of the web application

• The web request did not show in the IIS log

• No error in the Application events

• A warning in the System events (Event ID 5011) saying

A process serving application pool ‘MyAppPool’ suffered a fatal communication error with the Windows Process Activation Service. The process id was ‘2688’. The data field contains the error number.

The details tab displayed the following information:

ProcessID

2688

6D000780

---

Binary data:

In Words

0000: 8007006D

In Bytes

0000: 6D 00 07 80

Teh Internets wanted me to debug IIS and my .Net application with IIS Diagnostics Toolkit, and Debug Diagnostic Tool, and IISState, and awe-inspiring how-to instructions.

Instead, I chose to add logging statements to the code that was affected by the error, and found that cause to be the statement

int theID = doc.AddImageHtml(html);

As it turns out (thank you SO, also here), you need to activate the Gecko engine in ABCpdf to work on (some) IE9 machines (as I said, the code works ok on Win7Pro, and I had recently updated the server):

doc.HtmlOptions.Engine = EngineType.Gecko;

Trying out the Gecko engine, the next result I got was

WebSupergoo.ABCpdf8.Internal.PDFException: ABCpdf cannot detect any printers. Gecko Engine requires a printer installed in the system. Usually, XPS Document Writer would suffice. Try also running the service as an interactive user. —> System.ComponentModel.Win32Exception: The RPC server is unavailable
at System.Drawing.Printing.PrinterSettings.get_InstalledPrinters()
at WebSupergoo.ABCpdf8.Internal.Gecko.DocAddGecko.get_DefaultPrinter()
— End of inner exception stack trace —
at WebSupergoo.ABCpdf8.Internal.Gecko.DocAddGecko.get_DefaultPrinter()
at WebSupergoo.ABCpdf8.Internal.Gecko.DocAddGecko.Preflight(Doc doc)
at WebSupergoo.ABCpdf8.Internal.Gecko.DocAddGecko.AddHtml(Doc doc, String html, Boolean paged, Int32 width, String& err)
at WebSupergoo.ABCpdf8.Doc.AddImageHtml(String html, Boolean paged, Int32 width, Boolean disableCache)
at WebSupergoo.ABCpdf8.Doc.AddImageHtml(String html)

After creating an XPS printer in control panel, the web application was finally able to generate PDF documents again.

According to the ABCpdf support page (6.29), the MSHTML rendering engine should be avoided for future applications:

Unfortunately with the official release of IE9 Microsoft released new documentation which says the IHTMLElementRender::DrawToDC function that was required has been deprecated. This is especially unfortunate given that there is no replacement for this function.

Given that Microsoft appears to be unwilling to support these interfaces we would strongly recommend that on new deployments you consider a move to the new Gecko-based HTML engine available in ABCpdf 8.