Then again you probably have not had to rebuild the post/thread cache often either. I am not sure how to resolve the error problem if you are getting it even when updating a small amount of posts per time.

I think you need to upgrade your hosting package.

I would not use the nix setting.

I don't use the nix setting
I've rebuilt thread and forum info after every upgrade, last one was October(? i think) (and there was NO posting after October - place is more or less private for me and a few friends, we just started posting again the last 2 or 3 days) before the one I did yesterday and then repeated today.

--------------- Added [DATE]1392240735[/DATE] at [TIME]1392240735[/TIME] ---------------

my 'other' vB4 site (same host but a different shared server) has none of these problems

It appears that your account does not have enough memory allocated to allow to run this process. On a dedicated server I would tweak my.cnf and php.ini but on a shared host I am not sure how you can solve this.

It looks like your host has you limited to 8 mb of memory and you need at least 16. Even 16 is very, very low for a vbulletin site. Perhaps this was something the host changed with the server updates. See if they will change it to 64 at least.

--------------- Added [DATE]1392243031[/DATE] at [TIME]1392243031[/TIME] ---------------

You can also go into maintenance and phpinfo and see what your memory limits are.

Thanks, Richie, I'll go check that... my plan is supposed to be 'unlimited' =S

--------------- Added 12 Feb 2014 at 19:26 ---------------

from maintenance>phpinfo:
PHP Version 5.3.28
Directive | Local Value | Master Value
memory_limit | 128M |128M

Your memory is fine in terms of php but your host needs to tweak your mysql configuration(my.cnf) if is maxing out so low and then restart mysql.

I don't think any shared host could give you unlimited memory though many offer free bandwith and storage.

Your host needs to tweak these in my.cnf

sort_buffer_size
read_buffer_size
read_rnd_buffer_size
join_buffer_size
max_connections

I sent them that message, Richie. LOL. They better love me ;)
Anyway from cPanel I garnered these numbers:

CPU Usage 0 / 100 %
Virtual Memory Usage 0 / 1024 MB
Physical Memory Usage 10.6 / 1024 MB
Entry Processes 0 / 15
Number of Processes 0 / 100
I/O Usage 0 / 1 MB/s
Disk Space Usage 10,039.21 / ∞
Monthly Bandwidth Transfer 535.45 / ∞

Do they tell you anything?

I was just looking for an idea of your server specs. This info doesn't show your mysql settings but it looks like they treat you decently in terms of memory. Hopefully they will tweak the database too.

Well they've been doing *something* to it, it's acting crazier than ever, not allowing 90% of the posts attempted - about 1 in 20 actually posts now; they did escalate my ticket but I'm not holding my breath.

The fixes I gave you did they help

I guess not =S this is what I get when I click 'submit post':
https://vborg.vbsupport.ru/external/2014/02/19.png