I'll have someone else address the Perforce issue. That may be a known problem we are having with their latest version.
As for the schema issue, SlickEdit uses the schema for validation and for color coding. So even if you turn off validation, SlickEdit will attempt to find the schema. If it can't locate it for any reason, you will get that error. To prevent the schema from being loaded, you can add the extension of the file specifying the DTD/schema to the def_xml_no_schema_list variable. Use the SlickEdit command line (press ESC in most emulations) and type "set-var" followed by Enter. type the name of the variable, in this case "def_xml_no_schema_list" and press Enter. SlickEdit will display the current contents of the variable and allow you to modify it.
This will suppress the loading of schema files for all files with the specified extension, which will prevent you from being able to validate files of that extension as well. If, you are having trouble loading a single schema or a few schemas, you can define a local directory to hold that schema. To do that, select Tools → Options → Network & Internet Options → URL Mappings from the main menu. Then add the URL for this DTD/schema and specify a directory where that file can be found.
We're looking at adding a new Notification icon for errors and warnings. Dialogs like this one will be displayed as pop-ups using that system, so they will be much less bothersome in the future.
