I'm playing on the 360.

I just helped out the Brotherhood by finding some parts for them and i decided to get an implant from the med clinic.

After i got the implant i noticed my DT was gone..No it wasn't at 0 there was a blank space where it used to be.

Reloaded an earlier save and it was still blank,then reloaded my two previous saves and it was blank also on both.

I still had a DT rating when i went into the brotherhood and i didn't check it again until after i got the implant.Somewhere inbetween is where it disappeared and i have already oversaved my 3 saves..Why?

Because i get sick and tired of every other NPC i come across becoming hostile to ED-E for no reason and having to reload so i oversave often.

Any idea what happened to the DT rating?

Strange, try switching you armor to something else a couple times and see if that brings it up. It's an issue I haven't heard of before.

I've tried that.

Its a no go.Still blank.

I KNOW! You equiped something that offers DR, and the DT spot would fade back and forth, but you unequipped it whilst it was on DR, just reequip it and wait for it to fad to DT from DR
DR granting equipment: Rebreather etc

I'll try that.

It could also be the rebreather, sometimes if you equip it, the armor value thing gets messed up. Try messing around with it and see if your armor value gets fixed.

I had the same.
To fix it I just saved, turned of the Xbox and turned it on and reloaded, and the DT was back again.

Happened to me as well.
Just restart your system and continue playing.

Yep that worked.

I've been wondering why my DT was all greyed out. Thanks Mako, you clever Deathclaw!.