This issue has been reported to Quality Engineering as SPR# MBLT8CCJ3 and is addressed in Interim Fix 1 for Notes 8.5.2 Fix Pack 1 (852FP1IF1), which is now available for download from Fix Central (direct links provided below).

Fix Information

Interim Fix 1 for Notes 8.5.2 Fix Pack 1 installs without failure by omitting a fix for the NSL issue highlighted below, but otherwise contains all other Notes 8.5.2 Fix Pack 1 fixes. 852FP1IF1 supersedes 852FP1. The NSL issue will be re-fixed in Notes 8.5.2 Fix Pack 2 to replace npnotes.dll during a reboot to avoid file lock conflict.

NSL fix omitted from 852FP1IF1
SPR# YGAO7UPHML - Under some circumstances Notes Single Login may delay windows logon because of a delay while interacting with Windows performance data on the local machine. With this fix, Notes Single Login will no longer look for performance data so it will not slow down Windows logon. (Technote #1405603)

Notes Standard Configuration

NOTE: Notes 8.5.2 Fix Pack 1 is still an option for users who do not use NSL or for users who would rather keep the NSL fix and work through the workarounds described below to install 8.5.2 Fix Pack 1.