Error after synaptic reload ... synaptic nolonger runs. (Knoppix 7.4.2)

[philo]

'aptitude update' ends with this error message, which synaptic will repeat after "reloading":

W: There is no public key available for the following key IDs:
7638D0442B90D010
W: There is no public key available for the following key IDs:
9D6D8F6BC857C906
W: There is no public key available for the following key IDs:
7638D0442B90D010
W: There is no public key available for the following key IDs:
9D6D8F6BC857C906
W: There is no public key available for the following key IDs:
7638D0442B90D010
W: There is no public key available for the following key IDs:
7638D0442B90D010
W: There is no public key available for the following key IDs:
7638D0442B90D010

Should we just ignore it and assume that the reload took place?