Zabbix proxy fails with a query.

[Pierreb]

I had a proxy 1.6 running before and upgraded it to 1.8.
After that i have this spammed in the zabbix_proxy.log

2525:20100401:114426.094 [Z3005] Query failed: [1054] Unknown column 'unique_dcheckid' in 'field list' [select druleid,iprange,name,unique_dcheckid from drules where proxy_hostid=0 and status=0 and (nextcheck<=1270115066 or nextcheck>1270115066+delay) and mod(druleid,1)=0]

Anyone know what this means or how to correct it?
Not sure if its related to a other problem i have that is the agent.ping is not working anymore from the proxy.
Its showing 15 hosts as unreachable even tho its possible to do normal pings and i can login to the machines.

The servers are all windows servers running version 1.6.6 of the agent.

[richlv]

database is not compatible between 1.6 and 1.8. as it's just proxy, remove its db aand re-create it (or just remove it and launch proxy again if using sqlite)