ORCAD Layout Errors although No DRC Errors flagged

[Testhaus]

ORCAD Layout Errors after autorouting, Although NO DRC Errors were flagged:
(Lay-Err1)
This Error was under silkscreen print and therefore not visible:
(Lay-Err1b)
This error shorted the the output of an fine pitch IC to VCC and destroyed it.

There were other errors:
(Lay-Err2,Lay-Err3)
which fortunately did not harm the circuit.


This is really worrying.

What causes these errors ?
How to avoid these errors ?
How can these errors be detected ?

Thanks, Dix