ListGrid.sort() returning false

[tomhj]

I'm using SmartGWT version 2.3 and have hit a problem. My code calls ListGrid.sort(String colName, SortDirection dir) which is returning false. According to the doc, sort() returns true if it worked. So why would ListGrid.sort() return false - meaning the sort failed?

This particular ListGrid is using virtual scrolling and has 883 rows in it. I've verified that the colName passed in is valid

I turned on 'debug' logging for ListGrid and ResultSet via the Developer's console. That results in two messages:

11:25:59.309:MUP5:DEBUG:ListGrid:isc_ListView$4_0:delaying adjustOverflow: childClear
11:25:59.434:MUP5:DEBUG:ResultSet:isc_ResultSet_1 (created by: isc_ListView$4_0):getRange(0, 33) satisfied from cache

The strange part about that is the "satisfied from cache" line seems to say that rows 0 - 33 were sorted from the cache. But the result set has 883 rows which should require the sort to be done on the server side.