Random CTD's

[Not A Tumour]

Every so often Pr will just crash. Sometimes its accompanied by an error message, sometimes it just crashes with no warning and no message. The game also sometimes crashes in the loading screen, always around the 13% mark. The loading screen crash never happens on the first map i join, but when that map finishes and the next one loads, it crashes. It crashes on every map, but particularly Beirut and Wanda Shan.
Specs are:
AMD Phenom II 955 Black Edition
4gb RAM
GTX 460 graphics card