fq doesn't return any results

[ZHANG Liang F]

Hi, 
I had field defined to store the location of a file:
<field name="path" type="string" indexed="true" stored="true" />

And the return value is something like:
<result name="response" numFound="25" start="0">
  <doc>
      <str name="path">E:\my_project\ecmkit\test</str> 
      ...

But when I try to filter the result by using fq, None of the following return 
any results:

1. &fq=path%3AE%3A%5Cmy_project%5Cecmkit%5Cinfotouch 
(org.apache.lucene.queryParser.ParseException: Cannot parse 
'path:E:\my_project\ecmkit\infotouch': Encountered " ":" ": "" )

2. &fq=path:"E:\my_project\ecmkit\test"  (return 0 result)

Please help to suggest.

Thanks in advance.