0.9.4 & r1897 locking up

Program starts fine, but only allows for limited use before locking up (est. 10 to 20 minutes). First noticed on 0.9.4 when my son was editing his own composition. Program freezes and shows 100% of Windows resources. We are using XP w/ SP2 on a 2.2GHz P4 with 512Mb of RAM. Sound is onboard, Intel / Dell MB. The r1897 prerelease actually seemed to be worse. Lockup w/ r1897 occurs when either editing or just playback of demo scores and sooner than 0.9.4.