When posting something with Flickr into my WordPress V1.5 I have learned that wpautop incedently puts a "p" tag around the "style" and "span" tags produced by Flickr. Also each line within the "style" section was filled with a "br" tag at the end.
While the latter I could switch off with $br=0, I had to add "style" (and BTW "span" as well) to lines 60, 61, 66, 70, 71, 73 and 74 to avoid the "p" tag at the named places.
I think adding "style" and "span" could be done in the next update by default. Addtionally, a new filter line should make sure that inside a "style" section no "br" tags are being put.