Searching through Trex--fails--pls help

Hi

I am using TREX 6.0 SP1 for Windows Server 2003 with EP SP2 ,patch 26.

I have configured TREX processes successfully and all test related to TREX installation is passing.I have configured EP default and Http servlet to access TREX process.That also doing fine.

Then I created index for the datasource that also got created successfully,as per the TREX Monitor

But When I am seraching by giveing wildchar * or any file name its giving following error

-

Search Failure

Error during search occurred - com.sapportals.wcm.WcmException: A received argument has an invalid value (Errorcode 18)

An unexpected severe error occurred during the search call. If the situation persists, inform your system administrator.

-

Suprisingly I was able to serach all content and properties before using the same process,But now its failing.Yeah I did deleted the index and queue entries through EP iviews also directly from

C:\Program Files\SAP\TREX_6\index

and C:\Program Files\SAP\TREX_6\queue

also some property file required related to my index like "index_service.propertiesdocbaseindex"

After delete I have restarted all process ,all works fine

Any body Pls help me to debug the problem..to know the exact problem...It seems TREX is unpredictable

rgds

Shovan