This article is from the comp.sys.acorn FAQ, by Paul Vigay with numerous contributions by others.
This is generally caused by upgrading machines fitted with slower CD Rom drives to RISC OS 4 and is caused by the CDFSSoftATAPI module trying to access the drive too fast. One remedy is to obtain a soft-loadable version of CDFSSoftATAPI from RISC OS 3.7, copy it into your !Boot.Choices.Boot.PreDesk directory and then *UNPLUG the CDFSSoftATAPI module in RISC OS 4.
Please feel free to email me if you encounter this problem because I encountered it myself upon fitting RISC OS 4.
 
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