I had a similar problem & we can discuss on xbobliv G,T.> Rottieweiler, Quick overview if U found 29, U have to go inti Data Hive Solo almost half wi thru level sedurity guard will jump down 2nd hole with U ( If it doesn't follow U thrn U don't have all 29 or U are playing Co-op) it has to be SOLO. Lastly to do it Co-Op you heve to go thru entire campaign(it can be on easy if U want , then transition into Data Hive. It took me lot of time to figure this out but it's the way.
Whem U get him to follow U, protect him an follow him to special room near flamethrower, & he'll show U in to where #30 is, Hill turn on U after some dilogue then U must kill him & U got it- ood Luck
If Ur Solo & U have 29 of them go right into Data Hive & he'll follow U down hole.
[Edited on 08.25.2011 7:36 AM PDT]