Ok, mystery solved. If anyone's interested, here is the deal:

The original executable was UPX-Compressed, and the UPX-unpacker I used damaged the import segment, resulting in the WS2_32.DLL imports being marked as KERNEL32 ordinal imports. I decompressed it now using PE-Explorer, and, hey presto, everything makes sense! Those mysterious calls are functions like send, connect, etc, from WS2_32.DLL.
Thanks for your help, anyway!