An internal server error is something that happens internally on the server. Check your server error log (where the actual error is written). Knowing what the exact error is will be very beneficial.
Here is the log (all about flickr or xmlrpc)
**.**.**.** http://www.szdavid.com – [08/Jan/2005:09:35:13 +0100] “POST /wordpress/xmlrpc.php HTTP/1.1” 500 604 “-” “Flickr”
**.**.**.** http://www.szdavid.com – [08/Jan/2005:09:35:36 +0100] “POST /wordpress/xmlrpc.php HTTP/1.1” 500 604 “-” “Flickr”
**.**.**.** http://www.szdavid.com – [08/Jan/2005:09:35:48 +0100] “POST /wordpress/xmlrpc.php HTTP/1.1” 500 604 “-” “Flickr”
**.**.**.** http://www.szdavid.com – [08/Jan/2005:09:45:43 +0100] “POST /wordpress/xmlrpc.php HTTP/1.1” 500 604 “-” “Flickr”
**.**.**.** http://www.szdavid.com – [08/Jan/2005:09:48:12 +0100] “GET /wordpress/xmlrpc.php HTTP/1.1” 500 604 “http://wordpress.org/support/topic.php?id=20287” “Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.5) Gecko/20041107 Firefox/1.0”
**.**.**.** http://www.szdavid.com – [08/Jan/2005:09:48:12 +0100] “GET /favicon.ico HTTP/1.1” 404 289 “-” “Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.5) Gecko/20041107 Firefox/1.0”
**.**.**.** http://www.szdavid.com – [08/Jan/2005:09:43:47 +0100] “GET /wordpress/xmlrpc.php HTTP/1.1” 500 604 “-” “-“
**.**.**.** http://www.szdavid.com – [08/Jan/2005:09:43:59 +0100] “GET /wordpress/xmlrpc.php HTTP/1.1” 500 604 “-” “-”
Are you using WP v1.2.x? If so, I believe that problem has been corrected in the v1.5 betas.
How to update without losing the modifications I have done in the administration interface (index.php and so on) ?
