If you get the same error with just syncing contacts, then it's not the "Deleted Items" issue. Have a look at the wiki entry linked from the first post in this thread - there's instructions there on enabling debug logging.
Apr 21 13:17:38 Nokia-N900-42-11 activesync[1383]: AsConfigReader: unable to read string value of parameter 4 in account ActiveSyncAccount1. Error 5 Apr 21 13:17:38 Nokia-N900-42-11 [1368]: activesync: modest_activesync_plugin_on_queue_changed(0) Apr 21 13:17:38 Nokia-N900-42-11 [1368]: activesync: modest_activesync_plugin_on_queue_changed: operation added Apr 21 13:17:38 Nokia-N900-42-11 [1368]: activesync: END modest_activesync_plugin_on_queue_changed Apr 21 13:17:38 Nokia-N900-42-11 [1368]: activesync: modest_activesync_plugin_on_operation_started(9, 0x9da20) Apr 21 13:17:38 Nokia-N900-42-11 [1368]: activesync: modest_activesync_plugin_on_operation_started() end Apr 21 13:17:38 Nokia-N900-42-11 activesync[1383]: get CfgConnDeviceId err=5, value= Apr 21 13:17:38 Nokia-N900-42-11 activesync[1383]: max Sync folders = 50 Apr 21 13:17:38 Nokia-N900-42-11 activesync[1383]: max GetItemEstimate folders = 50 . . . Apr 21 13:17:38 Nokia-N900-42-11 activesync[1383]: AsConfigReader: unable to read string value of parameter 0 in account ActiveSyncAccount1. Error 5 Apr 21 13:17:38 Nokia-N900-42-11 activesync[1383]: get CfgConnExchangeServer err=5, value= Apr 21 13:17:38 Nokia-N900-42-11 activesync[1383]: CurlConnectionManager: cannot get CfgConnExchangeServer Apr 21 13:17:38 Nokia-N900-42-11 activesync[1383]: get CfgConnPort err=0, value=443 Apr 21 13:17:38 Nokia-N900-42-11 activesync[1383]: get CfgConnSecureConnection err=0, value=1 Apr 21 13:17:38 Nokia-N900-42-11 activesync[1383]: AsConfigReader: unable to read string value of parameter 5 in account ActiveSyncAccount1. Error 5 Apr 21 13:17:38 Nokia-N900-42-11 activesync[1383]: get CfgCredUsername err=5, value= Apr 21 13:17:38 Nokia-N900-42-11 activesync[1383]: CurlConnectionManager: cannot get CfgCredUsername Apr 21 13:17:38 Nokia-N900-42-11 activesync[1383]: AsConfigReader: unable to read string value of parameter 6 in account ActiveSyncAccount1. Error 5 Apr 21 13:17:38 Nokia-N900-42-11 activesync[1383]: get CfgCredEncryptedPassword err=5 Apr 21 13:17:38 Nokia-N900-42-11 activesync[1383]: CurlConnectionManager: cannot get CfgCredEncryptedPassword Apr 21 13:17:38 Nokia-N900-42-11 activesync[1383]: get CfgCredDomain err=0, value= Apr 21 13:17:38 Nokia-N900-42-11 activesync[1383]: mCertdir='/etc/certs/common-ca:/home/user/.maemosec-certs/ssl-ca' . . . Apr 21 13:17:38 Nokia-N900-42-11 activesync[1383]: get CfgMailSendPolicy err=0, value=0 Apr 21 13:17:38 Nokia-N900-42-11 activesync[1383]: AsConfigReader: unable to read string value of parameter 5 in account ActiveSyncAccount1. Error 5 Apr 21 13:17:38 Nokia-N900-42-11 activesync[1383]: get CfgCredUsername err=5, value= Apr 21 13:17:38 Nokia-N900-42-11 activesync[1383]: SyncScheduler: cannot get CfgCredUsername Apr 21 13:17:38 Nokia-N900-42-11 activesync[1383]: AsConfigReader: unable to read string value of parameter 0 in account ActiveSyncAccount1. Error 5 Apr 21 13:17:38 Nokia-N900-42-11 activesync[1383]: get CfgConnExchangeServer err=5, value= Apr 21 13:17:38 Nokia-N900-42-11 activesync[1383]: CurlConnectionManager: cannot get CfgConnExchangeServer Apr 21 13:17:38 Nokia-N900-42-11 activesync[1383]: CurlConnectionManager: haveAccount=0