If you can't taste salt - its an indication that you are severely salt deficient and unless you take salt quickly, coma and death an follow.
To put that in perspective it is a very uncommon situation, but exercising in hot climates can lead to salt deficiency - caused by rehydrating with plain water, which dilutes the salt reserves, so you should rehydrate with an isotonic drink. A friend of mine (a medic) experienced this while cycling in France.
Puts on Admin/Mod hat - I have removed some of the less relevant posts in this thread.