Sharepoint Partial Filename Search Fails

[mattmoney]

Hello, I have a sharepoint site with about 1500 docs in it, a mixture of office docs and pdfs and it's mostly ok but the search is failing on some of the pdfs. Using 'contains' if you search for the first half of the name some of the pdfs are missing from the search results. However if I use three quarters of the name or more then the files are there in the search results. What is weird is if I use the second half of the name then they appear in the search results. The files are clearly being captured in the crawl but there is some issue somewhere.

If anybody can help with this I'd be most grateful.

Thanks

Matt