Cannot start it!

I always get "Another instance of Firefox is already running. Please close other instances of Firefox before launching Portable Firefox.". Title of the error is "Portable Firefox - your browser ...". I think it's about the launcher.

That's the default "PortableFirefox.ini":

[PortableFirefox]
FirefoxDirectory=firefox
ProfileDirectory=profile
PluginsDirectory=plugins
UserProfileDirectory=userprofile
AdditionalParameters=
AllowMultipleInstances=false
SkipChromeFix=false
SkipCompregFix=false
WaitForFirefox=false
FirefoxExecutable=firefox.exe
DisableSplashScreen=true

I tried starting it, using:

[PortableFirefox]
FirefoxDirectory=firefox
ProfileDirectory=profile
PluginsDirectory=plugins
UserProfileDirectory=userprofile
AdditionalParameters=
AllowMultipleInstances=true
SkipChromeFix=true
SkipCompregFix=true
WaitForFirefox=true
FirefoxExecutable=firefox.exe
DisableSplashScreen=true

I restarted my computer many times,
tried to run it locally,
re-installed it,
used default profile,
used modified profile,
any left?

I can open AbiWord, Thunderbird etc. (Both Normal and Portable vers.)
I can open Firefox 1.5 (Local vers.)

I have PIII 600Mhz 64Mb RAM 10Gb HD(1.80Gb free) 1024Mb Flash Disk(756Mb free)
I use Windows98

Is there ANOTHER WAY to bypass this check