Please, can you test this :

-Add a clip to TimeLine (video WITH audio).
-Right click the Event and choose "Select in Project media list"
-Right click the media and choose "Replace"
-Choose a media WITHOUT audio (video only) to replace the media.
-Now, right click the Event on Timeline and choose "Open in Trimmer" > Vegas Crash and close.

______________________
Sony Vegas Pro 8.0
Version 8.0b (Build 217)
Exception 0xC0000005 (access violation) READ:0x1C IP:0x51B0C0
In Module 'vegas80.exe' at Address 0x400000 + 0x11B0C0
Thread: GUI ID=0xB04 Stack=0x12F000-0x130000
Registers:
EAX=00000000 CS=001b EIP=0051b0c0 EFLGS=00010246
EBX=088e21b0 SS=0023 ESP=0012f4b8 EBP=01e96460
ECX=00000000 DS=0023 ESI=00000001 FS=003b
EDX=0012f4f0 ES=0023 EDI=088e3008 GS=0000
Bytes at CS:EIP:
0051B0C0: 8B 51 1C 8B 44 24 08 89 .Q..D: 10 66 8B 51 20 8B 44 24 .f.Q .D
Stack Dump:
0012F4B8: 00525201 00400000 + 125201 (vegas80.exe)
0012F4BC: 01E97C48 01DA0000 + F7C48
0012F4C0: 0012F4F8 00030000 + FF4F8
0012F4C4: 0012F4F0 00030000 + FF4F0
0012F4C8: 0012F4E8 00030000 + FF4E8
0012F4CC: 0012F4E0 00030000 + FF4E0
0012F4D0: 7E39BB2F 7E390000 + BB2F (USER32.dll)
0012F4D4: 096E0170 09490000 + 250170
0012F4D8: 01E96460 01DA0000 + F6460
0012F4DC: 05413D68 05400000 + 13D68
0012F4E0: 00000000
0012F4E4: 00000000
0012F4E8: 00000002
0012F4EC: 00000000
0012F4F0: 00000000
0012F4F4: 00000000
> 0012F534: 004E15EE 00400000 + E15EE (vegas80.exe)
0012F538: 088E21B0 08880000 + 621B0
0012F53C: 095D57B8 09490000 + 1457B8
0012F540: 00000000
0012F544: 057F0F50 05400000 + 3F0F50
> 0012F5A8: 7C91EE18 7C910000 + EE18 (ntdll.dll)
> 0012F5B8: 7C942124 7C910000 + 32124 (ntdll.dll)
> 0012F5EC: 0053004D 00400000 + 13004D (vegas80.exe)
> 0012F5F0: 00530020 00400000 + 130020 (vegas80.exe)
> 0012F5F4: 00650068 00400000 + 250068 (vegas80.exe)
> 0012F5F8: 006C006C 00400000 + 2C006C (vegas80.exe)
- - -
0012FFF0: 00000000
0012FFF4: 00000000
0012FFF8: 0083F20B 00400000 + 43F20B (vegas80.exe)
0012FFFC: 00000000
______________________