[Sony Ericsson XPERIA X10 Mini] belovits:
Hmm, this is my build.prop after the update if it helps:

##### Final patch of properties #####
ro.build.product=SonyEricssonU20i
ro.build.description=U20i-user 1.6 1.2.A.1.174 406 test-keys
ro.build.display.id=1.2.A.1.174

ro.product.brand=SEMC
ro.product.name=U20i_1238-0199
ro.product.device=SonyEricssonU20i
ro.product.board=delta
ro.build.version.incremental=6
ro.build.tags=release-keys
ro.build.fingerprint=SEMC/U20i_1238-0199/SonyEricssonU20i/delta:1.6/1.2.A.1.174/6:user/release-keys

######################## Customized property values #########################

ro.semc.version.cust=1238-0199
ro.semc.version.cust_revision=R3A
ro.drm.active.num=3
ro.drm.active.0=semc,0
ro.drm.active.1=viaccess,0
ro.drm.active.2=marlin,0
ro.semc.ecclist.num=1
ro.semc.ecclist.type.0=Police
ro.semc.ecclist.number.0=999
ro.semc.ecclist.plmn.0=234 FFF
#########################################################################

ro.config.ringtone=sony_ericsson.ogg
ro.config.notification_sound=notification.ogg
ro.semc.content.number=PA8

################# Updating of the SW Version #################
ro.semc.version.fs_revision=1.2.A.1.174
ro.build.id=1.2.A.1.174

##### Values from product package metadata #####
ro.product.model=U20i
ro.semc.ms_type_id=AAD-3880072-BV
ro.semc.version.fs=WORLD-1-8
ro.semc.product.name=X10 mini pro

# begin build properties
# autogenerated by buildinfo.sh
#ro.build.id=1.2.A.1.174
#ro.build.display.id=1.2.A.1.174
#ro.build.version.incremental=406
ro.build.version.sdk=4
ro.build.version.codename=REL
ro.build.version.release=1.6
ro.build.date=Fri Jul 2 13:25:20 2010
ro.build.date.utc=1278069920
ro.build.type=user
ro.build.user=SEMCUser
ro.build.host=SEMCHost
#ro.build.tags=test-keys
#ro.product.model=mimmi
#ro.product.brand=generic
#ro.product.name=mimmi
#ro.product.device=mimmi
#ro.product.board=mimmi
ro.product.cpu.abi=armeabi
ro.product.manufacturer=Sony Ericsson
ro.product.locale.language=en
ro.product.locale.region=GB
ro.board.platform=
# ro.build.product is obsolete; use ro.product.device
#ro.build.product=mimmi
# Do not try to parse ro.build.description or .fingerprint
#ro.build.description=mimmi-user 1.6 1.2.A.1.174 406 test-keys
#ro.build.fingerprint=generic/mimmi/mimmi/mimmi:1.6/1.2.A.1.174/406:user/test-keys
# end build properties
#
# system.prop for mimmi
#

rild.libpath=/system/lib/libril-qc-1.so
rild.libargs=-d /dev/smd0
wifi.interface = tiwlan0
ro.semc.fm_service=1
ro.semc.def_screen_orientation=sensor
ro.semc.timescape_keys=X10_mini_pro_key
ro.sf.lcd_density=120
persist.rild.nitz_plmn=
persist.rild.nitz_long_ons_0=
persist.rild.nitz_long_ons_1=
persist.rild.nitz_long_ons_2=
persist.rild.nitz_long_ons_3=
persist.rild.nitz_short_ons_0=
persist.rild.nitz_short_ons_1=
persist.rild.nitz_short_ons_2=
persist.rild.nitz_short_ons_3=
persist.cust.tel.eons=1
persist.ro.ril.sms_sync_sending=1
DEVICE_PROVISIONED=1
# Constant values for Battery test in Service menu.
ro.semc.batt.capacity=950
ro.semc.batt.test.consumption=150
ro.semc.batt.test.z_threshold=50
ro.semc.batt.test.min_level=60

ro.qualcomm.proprietary_obex=1

#
# ADDITIONAL_BUILD_PROPERTIES
#
#ro.config.notification_sound=F1_New_SMS.ogg
ro.com.google.clientidbase=android-sonyericsson
ro.com.google.clientidbase.yt=android-sonyericsson
ro.com.google.clientidbase.am=android-sonyericsson
ro.com.google.clientidbase.vs=android-sonyericsson
ro.com.google.clientidbase.gmm=android-sonyericsson
ro.url.legal=http://www.google.com/intl/%s/mobile/android/basic/phone-legal.html
ro.url.legal.android_privacy=http://www.google.com/intl/%s/mobile/android/basic/privacy.html
ro.com.google.locationfeatures=1
ro.setupwizard.mode=DISABLED
ro.com.google.gms_preload_version=1.6_r16
#ro.drm.active.num=4
#ro.drm.active.0=semc,1
#ro.drm.active.1=cmla,0
#ro.drm.active.2=viaccess,0
ro.drm.active.3=marlin,1
ro.drm.whitelist.num=4
ro.drm.whitelist.domain.0=roap.drm.coremedia.com
ro.drm.whitelist.domain.1=.teslan.com
ro.drm.whitelist.domain.2=selddrmt02.teslan.com
ro.drm.whitelist.domain.3=.inovatel.com
ro.config.sync=yes
net.bt.name=Android
dalvik.vm.stack-trace-file=/data/anr/traces.txt
#ro.semc.version.fs_revision=1.2.A.1.174

Not sure what would happen if you use this one and try a repair?

But I recommend to backup your build.prop before you try...