NAV2009 WS Parameter x in method y in service z is null!

Remco
Remco Member Posts: 81
edited 2015-03-17 in NAV Three Tier
I published a codeunit as a webservice in NAV2009R2. The method of the codeunit has a parameter of type bigtext.
The application that calls the webservice get's the error Parameter xMLText in method CreateUpdateRecords in service XRMUpload is null! while it is sending xml data.
I have tried several things, like compiling the codeunit, restarting the service, but the error is still there. I did some searching on the mibuso forum, but did not find the answer.
Has anybody any idea how to solve this issue, or at least how to approach it.