I often get errors from this plugin akin to:
Code:
L 05/20/2012 - 19:55:03: [SM] Native "SetEntProp" reported: Entity 21 (21) is invalid
L 05/20/2012 - 19:55:03: [SM] Displaying call stack trace for plugin "TF2 Set Class.smx":
L 05/20/2012 - 19:55:03: [SM] [0] Line 306, /groups/sourcemod/compiler-1.3/include/tf2_stocks.inc::TF2_SetPlayerClass()
L 05/20/2012 - 19:55:03: [SM] [1] Line 125, /home/groups/alliedmodders/forums/files/9/4/3/2/5/97175.attach::Command_Setclass()
Since my admins use this a lot, hopefully a fix for this will be out soon.
Edit: Using latest version (1.2.1)