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I get this error message if I try to compile Zeos.

Zeos version: 7.1.3a stable
Lazarus version: 1.2.4
FPC version: 2.6.4
SVN Revision: 45510
Windows 64 bit

What means that error and how can I solve?

Please clean up all old compiled dcu's etc. and build all sources again. It works nice!

what do you mean with clean? What exactly I have to do?