I've sorted the problem. Unfortunately, you'll need to convert your original data (via the converter program in the following download) and replace your old B'lox! file. Download the following, extract and place both .gpe files into your Wiz's B'lox! folder.
http://www.iprice.re...ff/blox_fix.rar (<840kb)
I recommend copying your PROFILE.CFG file (in the Data folder) before doing anything, just in case the converter doesn't work properly.
Do not run the new B'lox! file yet, as it WILL crash.
Run the "Blox Converter" file via the Wiz Launcher. This will update your save file (hopefully keeping all data intact) to allow you to save upto 999 levels. It takes only one second to do it's stuff. Press a key to exit. You should only need to do this once, then you can delete the converter.
Now you can run B'lox! If it crashes, then the converter didn't do it's job properly. Do the above again.
All being well and good, your old data will still be present and you'll be able to save your progress on any level (upto 999).