The Decklink Extreme, whilst being versatile, does have a few issues:
The wiring loom causes an impedance mismatch with incoming SDI - especially long runs. If you are using the Extreme with a long SDI run, it is prudent to reclock the SDI before you stick it into the card.

Its worth checking that you have NO other software installed or running when you are running Catalysts. Some applications run daemons in the background which can detract from performance - video input perfomance is one area that can be effected.

The BlackMagic Decklink capture application that installs itself into applications when you install your decklink drivers is a useful diagnostic tool. If you shut down Catalyst and start up the capture application, it will show you what the card is seeing - which in turn is what Catalyst is seeing. A visible delay witnessed in the application means that the delay is from somewhere else. Remember that every bit of video equipment in the video chain - vision mixers, dve, routers/switchers, scan converters etc all add their own delays into the video signal.

I have tested most of the Blackmagic, Aurora Pipe cards with SDI, Composite, Y/C (where appropriate) and Component video in PAL and NTSC.

Best wishes,

Hugh
High End Catalyst test bloke.