Undefined index: LBL_VCAL_PERIOD

[sugarcm]

hi all,
sugar is extremly slow. so i turned on the logging in the admin setting:
log memory usage and
log slow queries and
show server answering time
then i get a lot of entries like:
Undefined index: LBL_VCAL_PERIOD occured in /srv/www/vhosts/sugar/cache/smarty/templates_c/%%7F^7F5^7F52877A%%EditView.tpl.php

with various index' missing.

surronding:
sugarCE-Full-5.2.0j
Linux Kernel 2.6.25.20-0 (x64)
mysql Ver 14.12 Distrib 5.0.51a

i did already the "repair" database and "repair index" from the admin - no changes.
is there a way to get those indices back alive?
the system is just newly setup so i can erase everything again as well.
the forum search did not lead to any recorded problem of that type (maybe it is not a problem :-)
i just thoght if performance is so low it could be a good idea to have all indices up and running...
any help is wellcome,
regards,
ula

[salesagility]

Have you got developer mode turned on?

[sugarcm]

i had not turned it on.
should i?
thanx,
ula