By default, The width of Select & Search prompt is fixed and therefore wide text will cut off.....
STEPS:
1) Locate for a File properties.js in the location ...c8\webcontent\prompting (on the machine where you installed cognos 8 gateway)
2) Take a back of it ( This backup is useful to restore the file properties.js if any thing goes wrong)
3) Open the file with any Text editor and search for the line..
"SYSTEMPROPERTY_CSEARCH_AUTO_RESIZE_RESULT_LIST=FALSE"
4) Replace FALSE with TRUE
5) Save the file
6) Launch the cognos and check the prompt you can see as follows..