Activision's biggest game of the year has inadvertently been shipped with code from one of the publisher's biggest rivals, according to a growing number of reports. Some versions of Call of Duty: Black Ops 2 are found to carry a second disc which appears to contain code for Mass Effect 2. A surge of video footage and forum posts from around the web shows that this means certain players cannot continue playing the game on PC due to not having the original second disc. The bizarre predicament appears to only affect PC customers. Activision's game discs which carry Mass Effect 2 data still show a Black Ops 2 cover mount, suggesting the problem is due to a disc manufacturing problem.