Unifrac and count table error message

I was trying to run unifrac.weighted on a tree generated through mothur and a count table that I created. However, mothur crashed and returned this error message.

mothur > unifrac.weighted(tree=andrew2.pick.chop.phylip.tre, count=andrew.count_table)

Using 8 processors.
Name: OTU_8256 is not in your groupfile, and will be disregarded.
[ERROR]: Your count table contains more than 1 sequence named OTU_8256, sequence names must be unique. Please correct.
error with lc

So, I checked my count table and actually there is no more than 1 sequence named OTU_8256. Not sure whats going on. Any help would be appreciated.

Can you try running the command set.dir(debug=t) before the unifrac command so you can see what mothur is reading?