cockblockery
The art and practice of cockblocking, generally in reference to intentional, rather than inadvertent, acts of cockblocking. However, this term can also be used to describe the tendencies of a person who possesses a certain oblivious demeanor that lends well to unintentional, albeit frequent, cockblocking activity.
This has to be at least the tenth time Stu has destroyed my chances. That guy's penchant for cockblockery knows no bounds.