When attempting to search for a line of text with Umlaut characters, like this:

Länderübergreifende

And the Indexing Language (Administration > General Configuration) is set to German, wildcard searches will fail to show the correct results.

Steps to reproduce:

1. Install a fresh new JIRA 6 instance.
2. Change the Indexing Language to German. Run a re-index.
3. Create a Project, and create an issue with Summary: "Länderübergreifende". Create another Issue with Summary: "Länderübergreifende2"
4. Search for this issue using the following JQL:

   summary ~ "Lä*"
   text ~ "Lä*"
   

   The results will show "Länderübergreifende2", but NOT "Länderübergreifende". However, search with

   summary ~ "Länderübergreifende"
   

   works without problems.

Now, change the indexing language to English/French/Other. (I have only tested 3) Re-index after you have changed the language. Run the same JQL queries as in step 4. The two issues will show up in the search results as expected.

Note that this does not happen if you search without Umlaut characters in your search query. For example,

1. Indexing Language: German
2. Search: "L*" will show both of the issues as expected.