File sharing and Permissions in Lion

[acme]

I can establish file sharing between my 2 Macs across ethernet.
Both are running 10.7.4

I can take files from and add files to, but I can't change the names of folders on the other computer. I type Admin passwords when asked, but ultimately I'm told I don't have permissions.

The folders in question are set to read/write on each computer, so that would seem to be A-OK.

Any thoughts? Apple tells me that Lion made file sharing more secure, but trickier to configure, owing to permissions issues, and that I could be in for a lot of tinkering to keep things running smoothly.

thank you for any thoughts on this.

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