vb.net - linq query cause System.AccessViolationException -

i have strange exception executing simple linq query, query expressed in vb.net (sorry..). exception is, title says: "system.accessviolationexception", full exception message chain

"system.web.httpunhandledexception: exception of type 'system.web.httpunhandledexception' thrown. ---> system.accessviolationexception: attempted read or write protected memory. indication other memory corrupt. "

the strange behavior is:

1. the exception thrown randomly
2. the exception thrown on production server , not on same test server
3. the query executed against production db using linqpad works perfectly

this full exception stack trace:

in stack trace erased methods calls makes query using single() linq method.

we think issue related kb installed on production server windows update, it's clear, dont't know exactly

any idea real issue? in advance

all symptoms points bad memory stick on server, or other hardware issues (overheating/overclocking). caused virus. access violations happen when pointer in memory gets corrupted , ends referencing protected memory area. recommend transfer image physical machine altogether , run full memtest86 run on server, , give housing thorough cleaning, replace old fans, etc... if problem not isolated way reinstall production server scratch on fresh drive.