[otrs] Sorting by a new field problem

Hello, I've customized the search functions to get the results to include a new customer field. There's no problem when I perform a search, but when I try to sort it (using the 'U' and 'D' links) the results are lost and I get an empty window. I don´t know if I've explained it well, I get these search results: Ticket ID (u/d) ... NewField(u/d) =================================== 1001 Test1 1002 Test2 If click u or d of 'NewField', I lose the results: Ticket ID (u/d) ... NewField(u/d) =================================== ----------Empty------------------- Any idea how I can solve this? Thanks in advance, J