This may be one of those bikes with a weird scandanavian bottom bracket, called a fauber bottom bracket. Not even sheldon mentions this style on his site.
You may need to get an adapter to adapt this to fit english thread bottom brackets
The link will send you to a finnish website, so you may need to call (the owner speaks english) to place an order.
After putting in the adapter, you should be able to use any standard english bottom bracket. Just want to make sure you get the right spindle length on the new BB. 107mm should probably work if you're running the chainring on the outer facing side of the crank spider, 110mm if you're bolting the chainring to the inside of the crank spider. Probably wouldn't be bad if you got a longer spindle than you needed though. Your crank may come with specs for a preferred spindle length.
See wikipedia entry about bottom brackets for more details.
Here is another link to fish for info: