I think the exact words you are looking for may be generated some other way, however based on what we know from Juniper so far, your error means exactly what you have similated, that there is a mismatch between the IKE phase 2 proposals. This is not like OSPF which tells you area mismatch:) I hope this helps you a little bit more.
9da4614f [0] / 0xfe8d052d } Info; Notify message version = 1
Aug 9 11:37:18 92.X.X.X:500 (Responder) <-> 94.Y.Y.Y:500 { 54f3cbfb 54471d6d - 87d62fbd 9da4614f [0] / 0xfe8d052d } Info; Error text = Could not find acceptable proposal
Aug 9 11:37:18 92.X.X.X:500 (Responder) <-> 94.Y.Y.Y:500 { 54f3cbfb 54471d6d - 87d62fbd 9da4614f [0] / 0xfe8d052d } Info; Offending message id = 0x00000000
Aug 9 11:37:18 92.X.X.X:500 (Responder) <-> 94.Y.Y.Y:500 { 54f3cbfb 54471d6d - 87d62fbd 9da4614f [0] / 0xfe8d052d } Info; Error text = Could not find acceptable proposal
Aug 9 11:37:18 92.X.X.X:500 (Responder) <-> 94.Y.Y.Y:500 { 54f3cbfb 54471d6d - 87d62fbd 9da4614f [0] / 0xfe8d052d } Info; Offending message id = 0x00000000
Aug 9 11:37:18 92.X.X.X:500 (Responder) <-> 94.Y.Y.Y:500 { 54f3cbfb 54471d6d - 87d62fbd 9da4614f [0] / 0xfe8d052d } Info; Received notify err = No proposal chosen (14) to isakmp sa, delete it
If phase 2 negotiation has been initiated, and you get the "Error = NO_PROPOSAL_CHOSEN" message, this indicates a mismatch in proposals between the two peers. The phase 2 proposal elements include the following:
Authentication algorithm (MD5, SHA1)
Encryption algorithm (DES, 3DES, AES128, AES192, AES256)
Lifetime kilobytes (sometimes referred to as lifesize)
Lifetime seconds
Protocol (AH, ESP)
Perfect Forward Secrecy (Diffie-Hellman group1, group2, group5)
If phase 2 fails to complete with an error in proposal, then confirm that remote peer has at least one proposal configured in which Authentication and Encryption algorithms, Protocol and Perfect Forward Secrecy (PFS) match at least one proposal on the local side. A common mis-configuration is PFS group key mismatch. Perhaps one side has PFS group key configured whereas the remote side may either not have PFS enabled or incorrect group key. Also, with some third-party non-Juniper devices, Lifetime in both kilobytes and/or seconds may also need to match.