Problems with Timeouts

I am using  LispWorks 4.2.0 and cl-http-70-156a-pre.

The form-function needs ca. 3 Minutes until it returns.
In a loop each customer is read from a file to a clos object.
After ca. 40 seconds and 120 customer read without error,
I got a strange error messages like 
   "Slot Nr is missing in <the customer object>".
If I read 100 customers and return in 20 Seconds, there is no 
error all. The same function runs during the initializing of 
the system with no error.
It seems to be  a timeout problem. I have increased the values
of :timeout and :livetime  in the export-url, but with no
success:

(export-url #u"/restart-kwg.html"
            :html-computed-form
            :form-function #'restart-kwg
            :expiration '(:no-expiration-header)
            :response-function #'respond-to-kwg
            :timeout    36000   ; 10 Min. [1/60   Sec.]
            :live-time 600000   ; 10 Min. [1/1000 Sec.]
            :public t
            :language :en
            :keywords '(:kwg :finance :credit-records-monitoring)
            :documentation "Read customers credit records.")

Helmut