v4.5.1 for N900 is available here.

Installation
1. Make sure you have latest Qt Mobility 1.2 libraries installed. If you have extras-devel repository enabled you can install those with "apt-get install libqtm-12=1:1.2.0+git20111104-0nd~fremantle5" or if you don't you can download libraries from here (and install with "dpkg -i libqtm-12_1.2.0+git20111104-0nd~fremantle5_armel.deb").
2. Download .deb file from the link above and install it.

Changes
- Bug fixes
- Improved WMTS support
- Support for other tile sizes than 256x256
- Automatic parser to parse WMS and WTMS server settings