NB partial file downloads blue but overall red

[g51]

NB starts downloading a multi-part rar file. In the "downloading files" list), when i click on the cross, i see that the children are being downloaded and their progress shown as blue, but the parent's is shown as red. In the logs, i see messages of "430-no such article" sorts. Why are the children shown as blue since they are "430"?

PS: at some point the download aborts with "too many errors"...