Micro SD Card Issue

Ok...so I had a 2GB card in my V3xx.  Moved it to the Z9.  No problems.  Recently purchased (2) 8GB Sandisk microSD cards...one for me as I was running out of room on my 2GB card...one for a friend.  I transferred files from 2GB card to 8GB card.  No problem.  Put it in the phone and seemed fine at first but then it started moving very slow....hit a button and wait for the screen to change.  Totally hung up once.  Turned phone off and back on...no difference.  Took 8GB card out....everything worked GREAT again.  So I transferred everything back to the 2GB card and put it back in....everything is GREAT.  Is this how they act when it's a bad card or is it because it's a large capacity card?  I will try the other one either tonight or in the morning to see if it does the same thing.  Anyone ever had this happen?