ORA-01785 error when dynamically resetting report source

Question

When programmatically changing the region source on a 'function body returning SQL query' report, i get the following error:
ORA-01785: ORDER BY item must be the number of a SELECT-list expression
if the new SQL statement has fewer columns than the one it is replacing, and the user had previously selected a sort column for a column# higher than the highest column number in the new query
for instance if the query was SELECT * FROM EMP and the user had clicked the COMM header to sort on COMM (column number 7), then changing the region source to SELECT * FROM DEPT results in the ORA-01785 -- evidently because Apex is submitting SELECT * FROM DEPT ORDER BY 7
is there a way to programmatically reset Apex's ORDER BY column# setting? clear cache and reset pagination don't seem to do it

Answer 1

that put me on the right track
i really didn't want to reset all user preferences, as i am making extensive use of them in this application
however, i did find HTMLDB_UTIL.REMOVE_SORT_PREFERENCES -- which, unfortunately, removes all sort preferences, not for a specific page or region.
i was able to find the correct preference in WWV_FLOW_PREFERENCES$, so I can user HTML_DB_UTIL.SET_PREFERENCE to reset it, but the preference_name includes the region#, which changes on import -- so i'll need to extract if at runtime using javascript, or figure out some other runtime technique for finding the correct preference_name
hey, apex developers, how about enhancing HTMLDB_UTIL.REMOVE_SORT_PREFERENCES to allow setting/removing the sort preference for a specific page (by page number or alias) and region (by position on the page or some other reliable identifier?