If you run WERCON, you should see a list of all recorded crashes, and the data that goes along with them. Even just the "appcrash" data that's shown there may be useful. For example, this is from one of my test boxes:
Product
payroll1.exe
Problem
Stopped working
Date
29-May-08 2:03 AM
Status
Not Reported
Problem signature
Problem Event Name: APPCRASH
Application Name: payroll1.exe
Application Version: 0.0.0.0
Application Timestamp: 483d7443
Fault Module Name: payroll1.exe
Fault Module Version: 0.0.0.0
Fault Module Timestamp: 483d7443
Exception Code: c0000005
Exception Offset: 0000280e
OS Version: 6.0.6001.2.1.0.256.1
<blah, blah>
Obviously, this has nothing to do with your problem except to illustrate the type of info you should find in WERCON regarding your Rundll32 crash.
Even better would be to configure WER (Windows Error Reporting) to generate a minidump during crashes, so that you can upload that minidump here and have someone look at it to try figure out what's happening to Rundll32.
If you're OK with poking around in the registry (don't do it if you're not confident), you need to add a REG_DWORD value called "DumpType" under this key:
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\Windows Error Reporting\LocalDumps
Set "DumpType" to be equal to 1, reboot, cause the Rundll32 crash again, and the new WERCON report should now mention a shiny new minidump.mdmp, by default saved here:
c:\users\<you>\AppData\CrashDumps