I have the same problem I'm on version 1.4.8 with the following settings : on system overviwe its everthing OK.

Operating System UNIX/Linux, Linux OK
PHP Version 5.4.4-14+deb7u14 (>5.3.8 recommended) OK
i-doit Code Version 1.4.8
i-doit Database Version 1.4.8 Revision 18308
Database size 25.38 MB
Browser (client) Mozilla/5.0, Gecko (Firefox/33.0) OK

how to solve the problem ???

att, Emerson Souza