Steps to reproduce:

1. Enter a search in the quick search bar with German special characters (i.e. ä,ö,ü)
2. The query string is changed on the result display, resulting in "No issues were found to match your search" (see attached screen shot)

Workaround: Use Advanced Search or use the stemmed version of the special characters (i.e. a, o, u)

The Bug was encountered after updating from JIRA 5.1 to 5.2 (following the manual step by step).