I saw a previous thread (now closed) that had this problem – that one was solved by installing a new version. In my case it was slow in 2.66 and remains very slow in 2.68. If i hit the open on a file browse button right after opening a blend, it comes right up. A few seconds later it will take so long i have to go away and come back again before i can browse for a file.
Are there any caches or temp files that blender relies on that might be causing this?