-Start the computer and hold down the CTRL key till the Windows 98 Startup menu
(boot menu) appears.
OR
- Repeatedly tap the F8 key after the memory count to bring up the boot menu.
-Use the arrow keys to select "Command Prompt Only" and press Enter.
-Type the following and press Enter:
scanreg /restore
Follow the prompts and select most recent rb###.cab file dated prior to the problem.

The backup files will be listed in rb###.cab format, and dated. The ###'s in the
file names won't be in date order. Don't use the one named rbbad.cab. Don't
restore a backup dated more than a couple of weeks old.

---

"If you still have boot problems after you reboot, you should use the command prompt
to edit the c:\windows\system.ini file. On the command line type: edit
c:\windows\system.ini

Once it is open, change the line shell=explorer.exe to shell=progman.exe. What you
are doing here is changing the default shell (that is having problems) from the
Windows Explorer to the old Windows Program Manager shell. Press Alt, F, S to save
the changes; then Alt, F, X to close.

"Reboot Windows. It should now successfully boot with no errors into an empty
Program Manager shell. Use the File | Run | Browse drop down menu selection to
browse to c:\program files\internet explorer (C:\Progra~1\Intern~1) or
C:\WINDOWS\Windows Update Setup Files (C:\Windows\Window~1) and launch ie5setup.exe
or ie6setup.exe (depending on what is there). (If neither of those files can be
found, you probably did not ever install IE from a download at Windows Update. In
that case, you will need to run ie6setup.exe from the CD you had installed from).
Do a Minimal-custom install and check all the Bold faced options. When the setup
program alerts you that these files are already installed, tell it to reinstall all
of the files.

When the Internet Explorer Setup program is done and reboots, hit the F8 key to
bring up a Boot Menu. Choose Command Prompt and boot to the command prompt. Once
there, type edit c:\windows\system.ini and, once it is open, change the line
shell=progman.exe back to shell=explorer.exe. Save and exit the file. You have now
set the shell back to the original value."

In der Registry unter Hkey Classes Root stehen die Dateinamenerweiterungen beginnend mit einem Punkt, z.B.
.AVI
der letzte Eintrag ist meist .ZIP
Die Liste durchschauen-wenn sich extrem lange Einträge finden (mehr als etwa 20 Zeichen, meist deutlich zu sehen, weil weit darüber), diese Löschen, dann stürzt die DLL nämlich ab.
Rechner neu Starten, voila, Problem gelöst

Running ie6setup from command line worked for me also. When Win98 reported Invalid Page Fault in SHDOC401.DLL at 0177:500054b2, I left the message unattended (i.e. do not hit close). Then, I did START/RUN => command to get command prompt. Then:
cd \ ... get to root directory
dir ie6setup.exe /s ... to find where ie6setup is on drive
-- on my drive, in C:\Program Files\Internet Exploder

Then change to directory with ie6setup and run it. Do custom installation and then select only IE6 browser from list of options to be installed. Once system is stabilized (as mine was after this) you can go back and install other options, if desired.

Re-installed IE6 using run->c:\programfiles\internet explorer\Ie6setup and found if typical install selected did not fix but select custon & specifically say the web browser & it worked fine.

Of course, upgrading or reinstalling IE will also help you out with your problem.