I think this will work.
Replace your loading function with this:
Code:
public LoadData(id)
{
new AuthID[35]
get_user_authid(id,AuthID,34)
new vaultkey[64],vaultdata[256]
format(vaultkey,63,"%s-FX",AuthID)
format(vaultdata,255,"%i#%i#",XP[id],CLASS[id])
nvault_get(g_vault,vaultkey,vaultdata,255)
replace_all(vaultdata, 255, "#", " ")
new playerxp[32], playerclass[32]
parse(vaultdata, playerxp, 31, playerclass, 31)
XP[id] = str_to_num(playerxp)
CLASS[id] = str_to_num(playerclass)
return PLUGIN_HANDLED
}