Ryan, my experiences were similar with the AMQ tapes. I didn't get the dirty head warning but got incredible amounts of dropouts suddenly, after quite a number of tapes with zero problems. It seems with those tapes there must be some manufacturing irregularities resulting in good and bad batches.

i believe sony always has good batches. and havent heard of bad batches ;)

the way the tapes are made....?
 

My film professor told my class only to use Sony tape due to the way that they are manufactured....

....I was a little skeptical of this particular instruction from him but maybe he's on to something :)