I had created a UltraGrid that had a hidden field that holds a rowid value. I was having a problem of converting the string value I was getting from the cell back to a rowid value. What I found was that I had to trim the returned string value before converting it to a rowid. See the code sample below.
cRecordRowid = ultraGrid1:ActiveRow:cells:Item:value
rwRecord = TO-ROWID(TRIM(cRecordRowid)).
MESSAGE cFrameClass cRecordRowid STRING(rwRecord) VIEW-AS ALERT-BOX.