Same results. I installed RW standard 2.5.0.3009 on my workstation but it still crashes instantly.
Process: RiffWorks [14991]
Path: /Applications/RiffWorks Standard.app/Contents/MacOS/RiffWorks
Identifier: com.SonomaWireWorks.RiffWorksStandard
Version: ??? (2.5.0.3009)
Code Type: X86 (Native)
Parent Process: launchd [188]
Date/Time: 2008-12-17 16:25:06.223 -0500
OS Version: Mac OS X 10.5.6 (9G55)
Report Version: 6
Exception Type: EXC_CRASH (SIGABRT)
Exception Codes: 0x0000000000000000, 0x0000000000000000
Crashed Thread: 0
Thread 0 Crashed:
0 libSystem.B.dylib 0x95651e42 __kill + 10
1 libSystem.B.dylib 0x956c423a raise + 26
2 libSystem.B.dylib 0x956d0679 abort + 73
3 libstdc++.6.dylib 0x93470005 0x93428000 + 294917
4 libstdc++.6.dylib 0x9346e10c __gxx_personality_v0 + 1108
5 libstdc++.6.dylib 0x9346e14b std::terminate() + 29
6 libstdc++.6.dylib 0x9346e261 __cxa_throw + 101
7 ...WireWorks.RiffWorksStandard 0x001e2ce8 0x1000 + 1973480
8 ...WireWorks.RiffWorksStandard 0x001e2f50 0x1000 + 1974096
9 ...WireWorks.RiffWorksStandard 0x001910f4 0x1000 + 1638644
10 ...WireWorks.RiffWorksStandard 0x00002f33 0x1000 + 7987
11 ...WireWorks.RiffWorksStandard 0x00002e8e 0x1000 + 7822
12 ...WireWorks.RiffWorksStandard 0x00002da9 0x1000 + 7593
Thread 0 crashed with X86 Thread State (32-bit):
eax: 0x00000000 ebx: 0x956d0639 ecx: 0xbffff7fc edx: 0x95651e42
edi: 0x00410554 esi: 0xa06785b8 ebp: 0xbffff818 esp: 0xbffff7fc
ss: 0x0000001f efl: 0x00000286 eip: 0x95651e42 cs: 0x00000007
ds: 0x0000001f es: 0x0000001f fs: 0x00000000 gs: 0x00000037
cr2: 0xa0381108
Hopefully support contacts me soon

It works fine on my old powerbook laptop, but it really hates my 8 core Mac Pro. RW T4 works fine on the same 8 core.