jQuery Grid Plugin - jqGrid

hi im testing jqGrid before deciding to use it in my productiion env.

works really well, its great.  i love also the possibility to reorder rows using  query.ui.sortable

anyway, i noticed a small problem: if i use sortable option, after i refresh the data, table seems to loose original column widths.

i tested in 

ie9 win 32 and 64 bits: perfect no errors

chrome win 32 and 64 bits : ERROR, every column widths is lost

firefox win 32 & 64: perfect no errors

firefox ubunto 32 bit: perfect no errors

firefox mac 64 bit: perfect.

mac safari 64 bit: ERROR, every column widths is lost

every browser is up to date with the last version oficially avaiable today, cache and and any other temp file are deleted deleted by theyr cache before testing.

this is my code:

jQuery("#jqG").jqGrid({

…..

colModel: [

                        { ...., width: jqWid($('#hidPageID').val(), 0, 220), ...  },        

......

 .jqGrid('sortableRows', ......);

i put online the page:

http://imenu.informarco.it/

enter with username : test

password: 222499390

then choose menu functions-->Archivio commesse-->Parametri commessa-->Tipo Asa

will appear the grid im talking about

thx for any suggestion