Blog import not working – please help!

Hi there. I posted this in Misc last week, but have been singularly ignored! I’d really appreciate it if someone could shed some light on this problem as I need to resolve it asap.
I have two wordpress blogs which I need to merge. I went to the old one and exported it as an xml file. Then I went to the new blog (which already has posts on it) and imported the file. I chose to map the posts to the existing users (because they’re all the same anyway) and selected to upload all links/ files etc. Then it appeared to import successfully; the list of imports appeared and my browser said ‘Done’. But when I viewed the blog and looked in the Posts, nothing had changed. The posts from the old blog have not been added to the new one. Am I doing something wrong?
Thanks.