I upgraded my IIS 7.5 web server to PHP 5.3.8 from PHP 5.2.17. After doing so, my Wordpress install started intermittently producing 500 errors:
HTTP Error 500.0 - Internal Server Error
C:\Program Files (x86)\PHP\v5.3\php-cgi.exe - The FastCGI process exited unexpectedlyDetailed Error Information
Module FastCGIModule
Notification ExecuteRequestHandler
Handler PHP53_via_FastCGI
Error Code 0x000000ff
I also run Drupal and the Zend Framework on this server, both of which use CURL, but these did not produce the error. As such, I'd say it's something specific to the Wordpress implementation of CURL.
I looked in the Windows application error log and found the following errors:
Faulting application name: php-cgi.exe, version: 5.3.8.0, time stamp: 0x4e537f4b
Faulting module name: php_curl.dll, version: 5.3.8.0, time stamp: 0x4e537f64
Exception code: 0xc0000005
Fault offset: 0x00036864
Faulting process id: 0x378
Faulting application start time: 0x01cccf17892cff0e
Faulting application path: C:\Program Files (x86)\PHP\v5.3\php-cgi.exe
Faulting module path: C:\Program Files (x86)\PHP\v5.3\ext\php_curl.dll
Report Id: ec31f1ab-3b0a-11e1-9d5f-005056b30014