How to make firefox extension compatible?

I have developed a firefox extension but firefox (v. 3.6.14) says the extension is not compatible with this firefox version.

I think my install.rdf is valid. It contains

<em:targetApplication>
      <Description>
        <em:id>{ec8030f7-c20a-464f-9开发者_StackOverflow中文版b0e-13a3a9e97384}</em:id> <!-- Firefox -->
        <em:minVersion>3.6.14</em:minVersion>
        <em:maxVersion>4.0.*</em:maxVersion>
      </Description>
 </em:targetApplication>

Any suggestions what could be the problem? What could cause this incompatibility?

---

I did not test it, but try to use the format

<em:maxVersion>4.0.0.*</em:maxVersion>

or

<em:maxVersion>4.0.*.*</em:maxVersion>

From https://developer.mozilla.org/en/extension_versioning,_update_and_compatibility:

Do not mistakenly think that * in a version represents any version. The * actually represents an infinitely high number and so is really only sensibly used in the maxVersion. Using it in a minVersion usually doesn't produce the effect you want.