With Speed Doubler 8 loaded I can't seem to shutdown or restart. I gives and error to quit all applications but to no avail. Any ideas?

I haven't seen any posts on Speed Doubler yet, but I am using the latest version and had to disable it because it would lock up during normal file copy procedures. By turning it off using Conflict Catcher (extensions manager will do the same), I got greater stability overall.

[nemesys]

I think I've read somewhere on Usenet that SpeedDoubler starts a background application and this application has problem when the Finder sends it a request to quit. This is caused by the increased memory requirement with 8.6. I know that the fix is to modify some resources in SpeedDoubler with ResEdit, but I unfortunately don't remember which exactly. I think it's the SIZE resource. The memory needs to be increased by about 300K. Do a search on Deja-News, in comp.sys.mac.system and you should find some info there.