Twice in the past few days I have experienced the same problem:
Nobody can connect via the concentrator and the only log entry I have in the concentrator is:
55004 10/12/2005 02:23:03.320 SEV=7 IPSECDBG/1 RPT=224 key_invalid_spi: passed a NULL address or spi
And the only way I can solve the problem is by rebooting the concentrator.
This is a 3030 with a 4.1.7.E software revision.
Any ideas?