OK so your portlets have something in the NSQL for them that says;
and some_table.id = @WHERE:PARAM:XML:STRING:/data/id/@value@
???
(thats is the same way "my" drill-down stuff works).
--
What version of 12 are you on; maybe thats a factor - I can certainly export to excel ok in a screen like that ok in my 8.1 instance but since I'm on 8.1 there I don't have the "page export" option available to me (which is the one you seem to have the problem with) (I'd have to experiment a bit to recreate my scenario in a 12.1 system so no quick response from me there I'm afraid).
FWIW I don't think that the gel/process bit is anything to do with it.... but to prove that, capture the URL in that screen shot. Log off Clarity, close IE, go make a cup of coffee, come back the next day (etc) - then open up IE and paste in the URL - does the problem still happen?