error When tried to Assign Filter for the field Severity

I am trying to retrive the severity defects list from QC using vb script. When tried to assign Severity as 'Level 1 - Critical', i am getting error. or at times the filter is not applied.

I am getting the count displayed as if i applied only first two filters. In one of the post, i learnt about 'Bug Status' table similary is there any table for bug severity from Customization.

Code below.

'tdc is connected to QC

    Set BugFactory = tdc.BugFactory
    Set BugFilter = BugFactory.Filter
    BugFilter.Filter("BG_DETECTION_DATE") > "11/5/2012"
    BugFilter.Filter("BG_STATUS") = arrDefectStatus(k) ' say 'Open', 'Close'

    BugFilter.Filter("BG_SEVERITY") = arrDefectSeverity(l) ' say ''Level 1 - Critical','Level 2 - High'

    Set BugList = BugFilter.NewList
    CountVal =BugList.Count

    msgbox CountVal