Leave it set to DIAG for normal flashing. Also check that you have MSXML 4.0 SP3 Parser and .NET Framework 3.5 installed before flashing.
There is some information about it in 4pda.ru forum: DIAG - standard flashing mode for phones which are turned on. EMERGENCY - mode for flashing phones in Emergency (Download) Mode. CS_EMERGENCY- same thing, but appears to be for non-working phones.
Samsung Galaxy S ROM: [slim].ONE.PT.XWJS5-v.3.0.0 KERNEL: SpeedMod K12A HZ=500 CWM] THEME: XWJS5.GingerONE-MOD.v.3 LAGFIX:SpeedMod LagFix ON & /system converted to EXT4 TWEAKS: BLN ON // Media Scanner Disable // all recommend
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