mail attachment does folder instead of file

Been using my MBP since new fall 2011 without issue. However, the last two weeks when I attempt to attach a single file to an outgoing apple mail email, the pop up window comes up where I have always drilled down in the folders to select a file.....it now doesn't drill down, but hangs up for about 5 minutes while it attempts to attach a massive folder that I clicked on to find the file. What is going wrong? Many thanks.