I have an ASA 5510 with cisco IPsec, but definitely sounds like same issue as me! luckily we have only like 30 macs, and like 90 PCs in the office and as we both said no issues on the PC side. For us it will be a huge PITA to change our work addresses, so I've been changing each home user's IP range that runs into issues. I've been doing some digging into this lately, and pretty much everything I've read says either the work or home network needs it's IP address changed.
