I have done some testing in multiplayer, and it seems to work fine on some servers.
On each of the tested servers I have made at least three attempts at spawning a Viggen, and rebooted the game after each attempt.
A list of the tested servers and what happened (Y = works, N = crashes, Y/N = works sometimes, crashes others):
Server Name
Outcome
Growling Sidewinder Open Conflict 1 of 4 Caucasus
Y/N*
Aerobatics Online Caucasus
Y
DCS Dogfighters - Dogfight Arena BFM |1v1|Fox2|BVR|Guns
Y
Aerobatics Europe
Y
Hoggit - Training Server
Y/N
Hoggit - Georgia At War
N
Through The Inferno -Dynamic PvE- [107th-SOCAL1]
N
Cold War 1947 - 1991
N
!!!PVE Server!!----by Stix
N
* If it crashes, the error "VIGGEN: HeatBlur: Assert failed: Value out of range. -. Was -6.003932. Expected between -3.141593 and 6.286327 @ c:\ajs37\trunk\viggennew\sources\flightmodel\aircraft.cpp:599)" can be found at the end of the log. This error is not present in my logs for any other server, nor in any of the logs others have uploaded in this thread or in this one, so it's probably a (slightly) different issue.
LOG_Aerobatics_Online_Working.txt
LOG_Aerobatics_Europe_Working.txt
LOG_Growling_Sidewinder_Working.txt
LOG_Hoggit_Training_Working.txt
LOG_Cold_War_Crashing.txt
LOG_Growling_Sidewinder_Crashing.txt
LOG_Hoggit_Training_Crashing.txt