ASP.NET: Parser error message with vbc.exe

Here's the scenario:

We have an ASP.NET powered Content Management System running on a server, which is built by a third-party and so unfortunately has to be considered a 'black box' for the purposes of this question. I don't know much about how it works. Its Windows 2008 with IIS 7.

For weeks it will work fine, and then suddenly it will start returning this .NET Parser Error whenever anyone tries to access a page:

Parser Error
Description: An error occurred during the parsing of a resource required to service this request. Please review the following specific parse error details and modify your source file appropriately. 

Parser Error Message: Cannot execute a program. The command being executed was
 "C:\Windows\Microsoft.NET\Framework\v2.0.50727\vbc.exe" /noconfig
   @"C:\Windows\Microsoft.NET\开发者_如何学编程Framework\v2.0.50727\Temporary ASP.NET Files\root\7082fc73\4a06ea64\iscamrh7.cmdline".

Source Error: 
Line 69:     <!--<%@ Register Src="/web/ContentLibrary/Section/section125.ascx" TagName="section125" TagPrefix="uc1" %><uc1:section125 ID="section125" runat="server" />-->
Line 70:     <%If useAltStyles Then %>
Line 71:      <%@ Register Src="/web/Tags/tag46.ascx" TagName="tag46_14" TagPrefix="uc14" %><uc14:tag46_14 ID="tag46_14" runat="server" />
Line 72:     <%Else %>
Line 73:      <%@ Register Src="/web/Tags/tag41.ascx" TagName="tag41_16" TagPrefix="uc16" %><uc16:tag41_16 ID="tag41_16" runat="server" />

The message mentions that it 'cannot execute' vbc.exe, which I know is involved with compiling aspx pages. And from the source lines it quotes, it happens when its trying to @Register custom controls on a page.

Does anyone have any hints or hunches on what might be causing this? E.g. is it the sort of thing that happens when the server is low on resources?

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For future reference, it turned out the be a memory shortage due to a memory leak in a COM component the site was using.

Setting a memory limit on the Application Pool recycle settings proved to be a temporary fix until the memory leak gets sorted.

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I don't know if the following is caused by copy/paste or truncated by the exception message but when I copy paste your aspx code in a new page I first get a compile time error that my "If" has to be terminated by "End If" but I don't see how this could cause the message you get. (tested with ASP.NET Development Server, VS2010 in ASP.NET 2.0 web project)

The second thing that strikes me is that the line

<!--<%@ Register Src="/web/ContentLibrary/Section/section125.ascx" TagName="section125" TagPrefix="uc1" %><uc1:section125 ID="section125" runat="server" />-->

although commented still needs the section125.ascx control to exist. Could it be that the error is generated inside the section125.ascx control.

Can you try to remove the commented @Register statement?