My construction set for TES IV Oblivion opens the way it should and works the way it should, but no matter what every time I attempt to save my progress the editor crashes immediately. Is this a common problem? What can fix this problem?

I don't know if it matters, but just in case I'm running Windows XP SP3, Pentium dual core 3 Ghz processor, 2 GB RAM, Nvidia GeForce 9400 GT graphics card. Oblivion itself runs perfectly, along with other games such as Half Life 2, Far Cry 2, Crysis, Morrowind, and the TES III Morrowind Construction Editor (which I can save with no problems).

Thanks in advance