Error while reverting from Field Permission back to Conent Permission module (Solved)

I came across this wonderful module "field permission" which can be used for more advanced permission settings for your contents. But then after sometime I realized that I needed to implement the Question/Answer module for my client. Now, the problem I faced was the Question/Answer module depends upon the "content permission module." With the "field permission" module already implemented, I was in a fix, because once I disabled the filter permission module and re-enabled the content permission I started getting queer error while accessing my Organic Group. Something like...

"user warning: Unknown column 'node_data_field_event_date.field_event_date_value' in 'where clause' query: SELECT COUNT(*) FROM (SELECT DISTINCT node.nid AS nid FROM d6_node node LEFT JOIN d6_og_ancestry og_ancestry ON node.nid = og_ancestry.nid INNER JOIN d6_node_access na ON na.nid = node.nid WHERE (na.grant_view >= 1 AND ((na.gid = 0 AND na.realm = 'all') OR (na.gid = 0 AND na.realm = 'og_public') OR (na.gid = 966 AND na.realm = 'og_admin')"

Few weeks back, I wasn't able to find the solution to this. But today while working around, I've found it.

What I noticed is that once you enable the Filter Permission module you are asked to uninstall the content permission module. And after enabling the Filter Permission module if you create a field_type
 (in my case I'd created even_date, which as you can see in the aforementioned query was the culprit for all the errors...) and again revert back to Content Permission module you will start getting errors like mine.

To solve this, try these two simple steps:

1. Go to "admin/content/node-settings" and REBUILD PERMISSIONS and see whether that solves your problem or not.
2. Else go to "admin/user/permissions" and look for filed (in my case field_event_date) that's causing the error and see whether the required permission is granted to roles such as "authenticated users" and guest or the role of your choice. If, not grant the required permissions and SAVE.

Your problem should resolve now.