I've been having trouble with cffile on a particular website. I created this as a test of a hypothesis. I think cffile's accept attribute is borked on CF10. I tested it on CentOS/Apache/CF10 Standard and localhosted on Win7. Go to http://steinbring.net for the explanation.

WithAccept.cfm

<form method="post" enctype="multipart/form-data">
	<input name="theFile" type="file">
	<input name="submitButton" name="submit" type="submit" value="Upload">
</form> 

<cfif isDefined("form.theFile")>
	<!--- Is there a file? Upload it to the files folder. --->
	<cffile action="upload"
			filefield="theFile"
			accept="application/vnd.openxmlformats-officedocument.wordprocessingml.document"
			destination="#expandpath('/mimetype/files')#"
			mode="775"
			nameconflict="Makeunique"
			result="local.UploadedFile">
	<cfdump var="#local.UploadedFile#">
</cfif>

<hr>

<!--- What file have you already uploaded? --->
<cfdirectory directory="#expandpath('/mimetype/files')#" name="qryDir" action="LIST" type="file">
<!--- Show them --->
<table>
<tr>
	<th colspan="2">Files that are uploaded</th>
</tr>
<tr>
	<th>Filename</th><th>Mimetype</th>
</tr>
<cfoutput query="qryDir">
	<tr>
		<td>#qryDir.name#</td><td>#FilegetMimeType(expandPath(qryDir.name))#</td>
	</tr>
</cfoutput>

</table>

WithoutAccept.cfm

<form method="post" enctype="multipart/form-data">
	<input name="theFile" type="file">
	<input name="submitButton" name="submit" type="submit" value="Upload">
</form> 

<cfif isDefined("form.theFile")>
	<!--- Is there a file? Upload it to the files folder. --->
	<cffile action="upload"
			filefield="theFile"
			destination="#expandpath('/mimetype/files')#"
			mode="775"
			nameconflict="Makeunique"
			result="local.UploadedFile">
	<cfdump var="#local.UploadedFile#">
</cfif>

<hr>

<!--- What file have you already uploaded? --->
<cfdirectory directory="#expandpath('/mimetype/files')#" name="qryDir" action="LIST" type="file">
<!--- Show them --->
<table>
<tr>
	<th colspan="2">Files that are uploaded</th>
</tr>
<tr>
	<th>Filename</th><th>Mimetype</th>
</tr>
<cfoutput query="qryDir">
	<tr>
		<td>#qryDir.name#</td><td>#FilegetMimeType(expandPath(qryDir.name))#</td>
	</tr>
</cfoutput>

</table>