Precision M6800 memory upgrade

I tried to install 2 x Crucial Ballistics 8GB 1866MHz memory modules to my Precision M6800 which Crucial claims to be guaranteed compatible. The system won't even start with them, individually or as a pair (without any other modules) but instead gives me error leds signaling "The memory modules are detected but has encountered an error".

I talked to Crucial and they still maintain that they should work and they have sold those to several M6800s. Are there any BIOS settings or something else that could change the situation? Or has anybody else tried those? The exact modules are these:

http://www.crucial.com/eu/search/searchresults.aspx?keywords=BLS8G3N18AES4CEU