------------Posted on Fri, Aug. 09, 2002 Keillor to exit downtown St. PaulBY BRIAN LAMBERTSt. Paul Pioneer PressWhat we can report for certain is that Garrison Keillor and the staff of "A Prairie Home Companion" are moving out of downtown St. Paul, and that Keillor has created a new corporate marquee for himself, Grand Prairie LLP.Beyond that, one is clearly meddling in the inner sanctums of Minnesota Public Radio, a regal, insulated place where Keillor and MPR president Bill Kling interact like co-doges of medieval Venice at the height of its empire.Sometime between the 15th and 30th of August, Keillor will...