I'd recommend changing the port back to 5555 if its at all possible.  We once required a different port because IIS was running a site under port 5555.  It worked in most cases but  caused us a fair amount of grief in the components that didn't smothly accept the different port.  We would have been much better off just changing the IIS port.

Looking at the following example:  http://help.k2.com/onlinehelp/k2blackpearl/devref/4.6.4/webframe.html#working_with_a_process.html  you wouldn't need to specify the port 5253 but only 5252.  In general K2 uses port 5252 to connect to the workflow and port 5555 (default) to basically everything else (smartobjects, environment library, etc).

If that doesn't help please submit your code so we can take a look.