Were you viewing any files using an external viewer?  I've found
that Firefox often `hangs' when opening a second PDF using xpdf --
until I quit the other xpdf instance.

I haven't investigated this further as I figured it was caused by
a plugin.  But it sounds kind of similar, so I thought I'd offer
this up just in case.

Brian.

-- 
  Brian de Alwis | Software Practices Lab | UBC | http://www.cs.ubc.ca/~bsd/
      "Amusement to an observing mind is study." - Benjamin Disraeli