Mike,
I'm curious what OS you are running, but here are a few things you can try...
If you have not tried to completely uninstall and reinstall, I would try that. (Make sure and export your settings to an INI file and back that up along with any scripts.
Also,
Do you have a \solarwinds\Kiwi Web Access\html folder anywhere?
If not, under your syslogd\setup folder, see if you have a file called: KiwiSyslogWebAccess_1.4.4_Setup.exe and try running that.
Failing to succeed with either of those suggestions, see if you can install it elsewhere and get the gateway.aspx file to install.