php-cgi.exe and/or php5.dll crashing - PHP 5.2.17, Win2k8 & IIS7

A specific part of my PHP script crashes randomly and I'm not sure why. The only difference on this page and the rest of the pages, is that I'm doing a PDO SQLSRV call. But 80% of the time there are no issues, and then suddenly IIS7 will just start spitting out the odd 500 error message. If I recycle the app pool, it works fine again for a while.

Here's the error from the NT log:

HTTP Error 500.0 - Internal Server Error
C:\PHP\php-cgi.exe - The FastCGI process exited unexpectedly

Detailed Error Information
Module  FastCgiModule
Notification    ExecuteRequestHandler
Handler PHP
Error Code  0x000000ff
Requested URL   {removed}
Physical Path   {removed}
Logon Method    Anonymous
Logon User  Anonymous

I'm running PHP 5.2.17 non thread safe, on Windows 2008 64-bit with IIS7. The IIS App pools is set to allow 32-bit applications, and as far as I can tell, FastCGI is configured properly in IIS and php.ini

Would really appreciate any suggestions people have. Thanks.

Windows also generated this crash report:

Version=1
EventType=APPCRASH
EventTime=129647371568690873
ReportType=2
Consent=1
ReportIdentifier=360d3929-058c-11e1-8a87-0050569801cd
IntegratorReportIdentifier=360d3928-058c-11e1-8a87-0050569801cd
WOW64=1
Response.type=4
Sig[0].Name=Application Name
Sig[0].Value=php-cgi.exe
Sig[1].Name=Application Version
Sig[1].Value=5.2.17.17
Sig[2].Name=Application Timestamp
Sig[2].Value=4d25fde8
Sig[3].Name=Fault Module Name
Sig[3].Value=php5.dll
Sig[4].Name=Fault Module Version
Sig[4].Value=5.2.17.17
Sig[5].Name=Fault Module Timestamp
Sig[5].Value=4d25fd3b
Sig[6].Name=Exception Code
Sig[6].Value=c0000005
Sig[7].Name=Exception Offset
Sig[7].Value=00009043
DynamicSig[1].Name=OS Version
DynamicSig[1].Value=6.1.7601.2.1.0.272.7
DynamicSig[2].Name=Locale ID
DynamicSig[2].Value=1033
DynamicSig[22].Name=Additional Information 1
DynamicSig[22].Value=0a9e
DynamicSig[23].Name=Additional Information 2
DynamicSig[23].Value=0a9e372d3b4ad19135b953a78882e789
DynamicSig[24].Name=Additional Information 3
DynamicSig[24].Value=0a9e
DynamicSig[25].Name=Additional Information 4
DynamicSig[25].Value=0a9e372d3b4ad19135b953a78882e789
UI[2]=C:\PHP\php-cgi.exe
UI[5]=Check online for a solution (recommended)
UI[6]=Check for a solution later (recommended)
UI[7]=Close
UI[8]=CGI // FastCGI stopped working and was closed
UI[9]=A problem caused the application to stop working correctly. Windows will notify you if a solution is available.
UI[10]=&Close
Loaded\Windows\SysWOW64\Kerberos.DLL
LoadedModule[60]=C:\Windows\system32\cryptdll.dll
LoadedModule[61]=C:\Windows\SysWOW64\msv1_0.DLL
LoadedModule[62]=C:\Windows\system32\ntdsapi.dll
LoadedModule[63]=C:\Windows\system32\LOGONCLI.DLL
LoadedModule[64]=C:\Windows\system32\security.dll
LoadedModule[65]=C:\Windows\SysWOW64\schannel.dll
LoadedModule[66]=C:\Windows\system32\mswsock.dll
LoadedModule[67]=C:\Windows\System32\wshtcpip.dll
LoadedModule[68]=C:\Windows\system32\ncrypt.dll
LoadedModule[69]=C:\Windows\System32\wship6.dll
LoadedModule[70]=C:\Windows\system32\DNSAPI.dll
LoadedModule[71]=C:\Program Files (x86)\Bonjour\mdnsNSP.dll
LoadedModule[72]=C:\Windows\system32\Iphlpapi.DLL
LoadedModule[73]=C:\Windows\system32\WINNSI.DLL
LoadedModule[74]=C:\Windows\system32\rasadhlp.dll
LoadedModule[75]=C:\Windows\System32\fwpuclnt.dll
FriendlyEventName=Stopped working
ConsentKey=APPCRASH
AppName=CGI // FastCGI
AppPath=C:\PHP\php-cgi.exe