I'm lol not because the problem of other ppl (your conclusion, Fat_Mike, about this is just stupid as hell), since there's no protection at all, you guys just have some bad installed modchip on your ps2, or your modchip is just bad.
Depends your laser and the media too (must be clean, and works pretty well).
I tested with over 10 ps2 here (all m2 pro modded by myself) and in all works fine, no problem at all.
SCPH-39001 v7 GH-022 NTSC U/C, Matrix Infinity v1.93 (installed by me), HDLoader v0.8c, Network Adapter (with SATA mod), 1TB SATA, SMS v2.9R4, VGA and GameLink 400 cables.
DEV1: uLaunchELF v4.42b / DEV2: CodeBreaker 10.1. Got PSX and PS3 too.
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