Fix STATUS_LPC_RECEIVE_BUFFER_EXPECTED (0xC0000705)

Quick answer: Restart the service or app throwing the error. If it comes back, run sfc /scannow then DISM /Online /Cleanup-Image /RestoreHealth — corrupt system files often cause this. Worst case, a driver reinstall or a registry fix for the LPC port timeout.

I first ran into 0xC0000705 on a client's Windows 10 Pro machine back in 2019. Their accounting software would crash every time they tried to print a report. The error popped up in Event Viewer under Application popup: STATUS_LPC_RECEIVE_BUFFER_EXPECTED. Turns out a third-party antivirus had hooked into the LPC (Local Procedure Call) port and wasn't passing a buffer back when the sync request came in. LPC is how processes talk to each other inside Windows — think of it as a pipe. One process sends a message, expects a reply buffer. If that buffer isn't there, you get this error. The fix isn't magic: you gotta find the process that's not playing nice.

What Actually Triggers This

This error shows up when a client app (like a database client, a printer spooler helper, or a custom business app) makes a synchronous LPC call but forgets to allocate or pass the receive buffer. Common triggers:

Corrupt system files in ntdll.dll or kernel32.dll
A rogue driver or filter driver (antivirus, backup software) intercepting LPC calls
A misconfigured registry key under HKLM\SYSTEM\CurrentControlSet\Services\ for a service using LPC
Memory corruption from a failing stick of RAM (rare but I've seen it)

Step-by-Step Fix

Identify the culprit process. Open Event Viewer (eventvwr.msc), go to Windows Logs > System. Filter by Event ID 1000 or look for the error code 0xC0000705. Note the Faulting module path. That's your target.
Restart the offending service. Open Services (services.msc), find the service tied to that module (e.g., Spooler for printing, SQL Server for DB). Right-click > Restart. If it's a standalone app, just close it and reopen.
Run System File Checker. Open Command Prompt as admin. Run sfc /scannow. Let it finish. If it finds corrupt files but can't fix them, move to step 4.
Run DISM. Same admin cmd: DISM /Online /Cleanup-Image /RestoreHealth. This fixes the component store that SFC depends on. Reboot after.
Check for driver updates. Open Device Manager, look for yellow triangles. Especially check storage controllers, network adapters, and any “Filter Driver” entries. Update them from the manufacturer's site — not Windows Update.
Test with a clean boot. Run msconfig, go to Services tab, check “Hide all Microsoft services”, then Disable all. Restart. If the error stops, one of those third-party services is the problem. Enable them one by one until you find it.

If the Main Fix Fails

If the error persists after steps 1–6, we're looking at something deeper.

Registry tweak for LPC timeout. Go to HKLM\SYSTEM\CurrentControlSet\Services\LanmanWorkstation\Parameters. Create a DWORD LpcTimeout (if it doesn't exist) and set it to decimal 60000 (60 seconds). Reboot. This gives LPC calls more time to set up the buffer — a band-aid, but works for some legacy apps.
Reinstall the app or driver. If the error points to a specific driver (like avc3.sys from a security suite), uninstall it completely using the vendor's removal tool, then reinstall the latest version. Had a client last month whose VPN driver caused this exact error — removed it, error gone.
Memory test. Run Windows Memory Diagnostic (mdsched.exe) and let it reboot and test. If it finds errors, replace the faulty stick. I've seen this error pop up randomly only on bad RAM.
System Restore. If the error started after a Windows Update or driver install, roll back to a restore point from before that change. Go to Control Panel > Recovery > Open System Restore.

Prevention Tip

Keep your drivers lean. Don't install “driver booster” tools or random system utilities that hook into Windows internals. Every filter driver adds another layer that can drop LPC buffers. I've seen printer software from HP and Canon do this. Use the built-in Windows drivers when possible. And run sfc /scannow monthly as part of your maintenance — catches corruption before it bites you.

“The LPC port isn't broken — something's blocking the buffer. Treat the blockage, not the port.”