That's what the verifying does: after dld has finished, it verifies the dlded file to see if a corruption has occured during the transfer. If it detects one, it will try to connect to hosts in order to download and correct the corrupted part of the data. It will do this up to 6 (is that right?) times. After that, if the corruption has still not been corrected, it will keep the data as it is but notify the user.
As Engel has pointed out, corruptions can cause various types of playback glitches: pops, ticks... In the worst cases, it will cause the player to read the corruption as a stop point and prompt it to stop playback (I had one of these. Incredibly annoying little *******.). In the case of videos, it can also cause the image to go weird for awhile or to just stop, while the soundtrack still plays... weird stuff...

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iMac G4 OSX 10.3.9
RAM 256MB
LW 4.10.5 Basic
ADSL anything from 3 to 8Mbps/around 1024kbps

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