Thanks I've found a solution for this problem. As this problem is easy to reproduce in Access 2010 and 2013 I'll post it here:
- This happens when the webbrowsercontrol is changed BEFORE the first DoEvents. (Form OnLoad, calling function directly after opening form)
Solution:
- set the control source to about:blank (prevent security warning and 404)
- a "DoEvents" BEFORE the .Open command