Hi, this is my very first patch, so be gentle.

Basically, the original function taxonomy_get_tree($vid,$parent,...) would treat $parent="0" the same as $parent=0, while the wrapper does not. This was causing me problems in conjunction with the content_taxonomy module. I don't know whether it is a bug that a string was being passed anyway, but the fact is that it worked in the taxonomy module, but not the category module.

I don't know how to produce .patch files, so I'll just write out the fix.
In /category/wrapper/taxonomy.module.copyme
Find the function taxonomy_get_tree
And change the first line
if ($parent === 0) {
to
if ($parent == 0) {