When I try to save an existing product it takes me to a blank page and the data is not getting saved.It does not happen for all products but only few.It was working fine until last week and haven't installed anything new. I tried error reporting in index and its not showing any errors. I have only system logs and have this warning - not sure its related to my issue.
Warning: simplexml_load_string() [function.simplexml-load-string]: Entity: line 64: parser error : Start tag expected, '<' not found in /home/magento/public_html/lib/Varien/Simplexml/Config.php on line 510
Current memory limit is 1024