Raid Cooldown/Lock

I completed TOC 10 man then joined a party for 25 man, i noticed that i had been locked out...
I asked other players if i will get locked out of 25 man if i complete 10 man of the same dungeon... they said 'no'

The same thing happened to me for VOA - i completed 10 man just now and joined a party for 25 man and then i was locked out of 25 man... i agained asked the people in my raid and they said you shouldnt be locked out...

Am i missing something ???
Thanks

My raid tab also shows the cooldown for both the instances - (10 man and 25 man for TOC and VOA) **ive never even entered toc 25 or voa 25 with this character before**