There are three different stages to deal with in this context, and many people are not aware of the different levels of seriousness of a hefsek (interruption) during these stages.
Usually, berachot precede the mitzvot that they are connected to. When it comes to netilat yadayim, however, we recite the beracha after washing because sometimes dirty hands prevent us from making the beracha beforehand.[1] In order not to introduce a hefsek between the main part of the mitzva and its subsequent beracha, one should not talk from when he starts to wash until he says the beracha.
The second stage, between the berachot of netilat yadayim and HaMotzi, is actually the least severe. We remain quiet and try to minimize the interruption between the two because of the gemara’s statement[2] that the beracha comes right after washing. However, there are different opinions about which washing the gemara is referring to (the other being the mayim acharonim before Birkat HaMazon).[3] In any case, even if one did speak, no beracha was severed from its mitzva, and there is thus no need to repeat anything.[4] It is only if one became so involved with other concerns that he forgot about keeping his hands clean that he needs to repeat netilat yadayim.
The final stage is the most stringent. The beracha of HaMotzi must directly precede the consumption of bread. Therefore, one should not stop, and certainly not speak, between the beracha and its referent, i.e., eating bread. If one talks about anything other than matters related to the food, he must repeat the beracha.[5] Since the beracha is linked to the main part of the eating process, namely, swallowing, one should not talk until that point.[6] However, since chewing is the beginning of the eating process, and it is usually accompanied by swallowing some of the food’s flavor, one does not repeat the beracha if he spoke after he started to chew.[7]