IIS6 / Server 2003 / Net 2.0 Apppool crash w3wp.exe - Help im going mad!

'Out of the blue' - our Server 2003  .Net 2.0 IIS6 webserver starts having issues.   Server 2003 4Gb memory etc....

When performing a PDF conversion which uses Websupergoo's  ABCpdf.dll to convert files into PDF format the request basically crashes the apppool,  which recycles and crashes again until it eventually times out.

This has been working fine for years, no updates to code etc.  This is happening to all sites on this webserver when they peform the conversion to PDF.

The same code works perfectly on another Webserver with IIS7.

I suspect something is wrong with the OS / ABCpdf - corrupted file or similar??

When I trigger the conversion,  the apppool balloons in memory slowly and then crashes after 30seconds or so then starts ballooning again - repeatedly until I get a timeout message in browser.

The event logs show :

EventID 4096
Assertion Failed in .\NDoc.cpp line 795 (*outErr == NULL).

I have looked at crashdumps etc with debug diagnostic tool :

Entry point   mscorwks!ThreadpoolMgr::intermediateThreadProc

Full Call stack:
Function                                         Arg 1                Arg 2                Arg 3     Arg 4   Source
kernel32!RaiseException+53     e06d7363     00000001     00000003     0297b39c    
msvcr80!_CxxThrowException+46     0297b3c8     79ee1048     854f0efa     0297ba9c  
f:\dd\vctools\crt_bld\self_x86\crt\prebuild\eh\throw.cpp @ 161

First chance exception 0XE06D7363.dmp the assembly instruction at kernel32!RaiseException+53 in C:\WINDOWS\system32\kernel32.dll from Microsoft Corporation has caused an unknown exception (0xe06d7363) on thread 18

I have tried to work out what's happening but 'unknown error'

Things I have done so far:

Repaired .Net 2.0
Repaired .Net 3.5
Re-installed ABDPDF
Run a disk scan on C system files.
Recovered space on drive.
I noticed tmp files are created in C:\windows\temp  by ABCpdf as part of the conversion process these files seem very small 18k - compaired to files previously of approx. 300k when PDF conversion was working.

Any help would be greatly appreciated im pulling my hair out.

Everything else seems to work without issue only the PDF conversion functionality failes/timesout and crashes the app pool.
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Najam UddinCommented:
Not sure if pdf being generated it too big, yet having 4 GB RAM doesn't mean ASP.NET gets to use it all.
Your can however try few tweaks
1. <processModel autoConfig="true" memoryLimit="80"/> in machine config. default is 60%.
2. Tweaking Maximum used memory (in megabytes) property on the application pool.

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Spikeuk30Author Commented:
Thanks for everyones help - in the end the only solution was to migrate the site to another webservers - no code changes were made, the PDF functionality 'just works' on another server.
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