ipsec between ASL and Wachguard Firebox is working. i have tried with ASL 2.0.16 and i guess i should also work with new 3.050. please note you need Release 5.01 on you Watchguard box !
the source of the problem with 4.61 is that the WatchGuard uses only single DES for IKE (Phase 1, Main Mode) keying. with 5.01 you can configure that option.