C:\Program Files (x86)\XyEnterprise\Contenta\Checkout\EpicEdit\IABCDE-0000-01-23-00-01A\111A-A_12345_67891_01\
IABCDE-0000-01-23-00-01A\111A-A_#12345_#67891_01.xml

WARNING: The stylesheet 'C:\XyEnterprise\Contenta\System\Schema\S1000D_4-0\proced.style' for document 
'IABCDE-0000-01-23-00-01A\111A-A_#12345_#67891_01.xml' does not exist or cannot be read.  [A30221] Ignoring stylesheet association.

WARNING:  Using stylesheet "C:\Program Files (x86)\XyEnterprise\Contenta\S1000D_samples\schemas\4.0\xml_schema_flat\proced.style".

1. Check out data module
2. Go to the checkout folder and open the xml file in an ascii editor.
3. In the XML file, there is a processing instruction with a path that points to a style sheet.  (If there is no processing instruction, you have a different problem.)
4. Go to Format Menu in Arbortext 
5. Choose "Select Stylesheets..."
6. click on Editor/Default
7. Remove "editor style sheet" file association 
8. save 
9. check data module back in 
10. Check the data module out again.
11. Go back to the checkout folder and open the xml file in an ascii editor, there will be no processing instruction in the file.