Yeah, that error's a pain. You're mid-deployment or troubleshooting a service and suddenly you see 0x8001010C. Let's cut straight to the fix that resolves it in 90% of cases.
The Quick Fix: Restart the COM Surrogate or the Service
Before you go down the rabbit hole of registry edits, restart the service that's throwing the error. In most cases it's a Windows service hosting a COM object, or the DCOM Server Process Launcher itself. Here's the command to restart the relevant service (run as admin):
net stop dcomlaunch && net start dcomlaunch
If that doesn't do it, restart the service that's actually crashing. Open Services.msc, find the service tied to the application (like World Wide Web Publishing Service for IIS, or the specific app pool), and restart it.
For IIS specifically, the culprit is often a worker process recycling that leaves a stale COM reference. Do this:
iisreset /restart
Why This Works
The error RPC_E_INVALID_CALLDATA means somewhere a COM interface call received data that didn't match what the interface expected. The classic scenario: a client process holds a reference to a COM object across a security boundary or a network hop. Between the call and the data marshaling, the object's state changed, or the proxy/stub got out of sync. Restarting the service clears all that stale state. It's the same reason you reboot a Windows box after a week of weirdness – it resets the COM runtime's internal tables.
In my experience, this error shows up most often on Windows Server 2016/2019/2022 when an application pool tries to instantiate a COM component that's registered under a different bitness (32-bit vs 64-bit) or when the component's DLL was updated without re-registering.
Less Common Variations: Re-register the Proxy/Stub DLL
If restarting didn't help, the next thing is to re-register the specific COM component. The error message often includes the CLSID or the interface GUID. If you have that, you can track down the DLL in the registry and re-register it.
- Find the CLSID – Check the Windows Event Log under Application. The source will be the component, and the details might mention
CLSID {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}. - Locate the DLL – Open regedit, go to
HKEY_CLASSES_ROOT\CLSID\{the-guid}\InprocServer32and note the default value – that's the DLL path. - Re-register – From an elevated command prompt, run:
regsvr32 /u "C:\Path\To\Your.dll"
regsvr32 "C:\Path\To\Your.dll"
That re-creates the registry entries and usually fixes the mismatch. Also, if the DLL is 32-bit and your service is 64-bit (or vice versa), you'll need to run the version of regsvr32 that matches – SysWOW64\regsvr32.exe for 32-bit on 64-bit systems.
When It's DCOM Permissions
Another variation: the calling service doesn't have the right permissions to invoke the COM object. You'll see that the error only happens when the service runs under a specific account (like NETWORK SERVICE) but not under SYSTEM. In that case, open dcomcnfg, find your component under Component Services, and give the account Launch and Activation permissions.
Prevention for Next Time
The root cause is often sloppy updates. Someone patches a DLL without running regsvr32, or an installer overwrites a proxy DLL without updating the registry. Here's how to avoid it:
- Always re-register after updates – If you're updating a COM component, make sure your deployment script includes the regsvr32 step.
- Monitor for bitness mismatches – Keep 32-bit and 64-bit components in separate folders and document which service uses which.
- Set up a watch on the Event Log – Create a custom view for Event ID 1000 or whatever your app logs, so you catch this before it bites a user.
Most times you'll never see this again if you restart services after any DLL change. It's a classic Windows quirk, but the fix is straightforward once you know where to look.