Ok, I've looked this up and asked 2 professional videographers. They told me the same thing, so I was hoping to get an answer here.

The footage was shot on a Sony Z7U on MiniDV tapes in High Def (30p). When I tried playing back the tapes on a Sony A1U, it kept giving me the message "Change to correct tape format." I tried everything to fix it. Changing from Auto-HDV-DV, 480i-480p-1080i, etc. Nothing works. What's awkward about it is that the tape plays on a blue screen even though it gives me that message. When I fast forward while in play, I can see the images.

Can someone please help?

The A1 doesn't do 30p. You need a playback device that does.

From the Z7 Manual, page 83:

Just to clarify for Bruno: While the A1U has a 30p mode, that is actually only "mock-30p" rather than true 30p. The A1U records 60i and uses firmware to generate a 30p output from the firewire port. The A1U cannot play tapes with true 30p recorded on them. The Z7 can record and play both the mock 30p and true 30p. If the Z7 recorded in true 30p, the A1U cannot play it back.

You need to use that Z7 to feed the footage to your computer.

Is the problem that that the Z7 not accessible or is this a matter of you not wanting to use Z7 because you think you need to protect its tape heads from wear? If the latter, stop worrying. The playback heads are different from the recording heads, and you won't shorten your Z7's life by using it as a deck.

And to further clarify, if you record "fake" 30p in the Z7 -- that is, 30p over 60i -- it'll play back just fine on the A1. You would set REC TYPE to INTERLACE but SCAN TYPE to 30.

Again, page 83.