I think this is what you're looking for: In the "Hatch Edit" window you will see the Scale set to 1.00000 - increase this number, let's say to 10 or 20 to start with. If you don't know how to get to the "Hatch Edit" window, simply double-click the hatch you want to edit, or right-click the hatch and slect "Hatch Edit...".
If it is the Hatch Scale problem, you could also change it using the Properties Palette: Select the Hatch, open PropPal (Ctrl+1), change the Pattern / Scale property. This would also allow you to change several hatches at once.
BTW, how do you create the Hatch? From a Tool Palette or through the Hatch command? If the TP then you may have to modify the scale it comes in as to not get this error again. If the command you may need to check your MEASUREMENT variable, if set to 0 the hatch-size is relative to Inches. If set to 1 the Hatch size is relative to milli-meters. Makes a bit of difference as placing Inch scaled hatches in Millimeter drawings are 25.4 times closer than expected.
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