Does anyone have experience using CourseLab with the Aspen/SumTotal LMS?

Unfortunately, we have no access to this LMS to check compatibility.
But, AFAIR, SumTotal LMS supports at least SCORM 1.2 and SCORM packages import. CourseLab generates SCORM-conformant packages, therefore CourseLab-generated content should work in this LMS. If you have access to this LMS you can check compatibility using our <a href="http://www.courselab.com/db/cle/B8EE5EAC2E729532C32572AB003A98AF/doc.html">LMS Test Package</a>.

I also want to use courselab with sumtotal, and although the course runs in the sumtotal LMS, there is not communication between the course and the LMS. That means although a course is passed sucessfully, the course is still shown as "ongoing" in the trainee transcript. My colleague (who uses toolbook) tells me I need to end a training presentation with an "exit page" to enable the communication between courselab and sumtotal, however I cannot find out how to create such an exit page. Any ideas?

AFIK hitting the [X] should push the variables to the LMS. Up to the point of doing this they are just hanging in the API waiting for something to happen.
An exit page just deos the same thing and pushes the variables. This would be a simple page just saying 'the end' or maybe with a button to trigger the action and then close the module OR just a page with a page level action.
If you had a few action statements like this
before display ~
if success=(your criteria)~
set success status.
Do the same for completion and score which should trigger the variables to be pushed out.

You might use
http://testtrack.scorm.com/ (read their state about copyrights!) to test the module.

The last lines of a test scorm package made in CL were:
LMSSetValue('cmi.core.lesson_status', 'completed') returned 'true'
LMSGetLastError() returned '0'
LMSCommit('') returned 'true'
LMSGetLastError() returned '0'
LMSFinish('') returned 'true'
Pre-evaluation of exit action
OverallSequencingProcess for SCORM 1.1 / SCORM 1.2

I suggest to make a test package, see what it does in Sumtotal and what it does in testtrack.

I know from another LMS that it doesn't react as it should on the 'standard' functions. A package which runs ok in Sumtotal and imported in testtrack should show which function is used for status = completed.

Another thing: I understood from Nick that some LMSses accept only a limited amount of data. Not sure if I understood right but Nick will tell ;-)
Can it be that the enormous amount of data CL send is too much?

Barend is correct that different LMS's do accept different volumes of data from the modules. The original specs set a fixed size which didn't really forsee the potential complexity of e-learning packages so the transfer size set was good for the time.
The actual ammount varies slightly from AICC, to SCORM and the varients of SCORM itself. Also some of the LMS providers have upped the ammount their systems accept, but not everyone has done this.
It does look like some LMS providers started with AICC and then just tagged the SCORM elements on rather than redevelop their products, can't blame them really as it would have been expensive to do and not made a significant or noticable change that could be 'sold' to the end users.
It might be worth trying the LMS test package as an AICC and a SCORM 1.2. You might find that works better