Attempting to run Reclassify on a floating point raster, where the raster is a constant value, produces the following error:
"Encountered a simple conflict when adding remap records."
This is a known issue with ArcGIS 9.2.
Run the Int tool located in ArcToolbox > Spatial Analyst Tools > Math, or ArcToolbox > 3D Analyst Tools > Raster Math to convert the constant floating point raster to an integer raster. Once the raster is in integer form, it can be reclassified using unique values.