_sessions table keeps crashing :(

[blablabla]

I've been using Coppermine for a long time now and never had any problems with it.
But last two days I don't know what's happening, I keep getting mysql errors and when I check database in phpmyadmin cpg132_sessions table is usully the one that's broken.
I don't know why this keeps happening, other scripts (WordPress and SMF) are still working without problems.
My host tells me that mysql is working ok but that there are too many queries and that I should see the code in my application to check whether any conditions that can cause looping of mysql queries occur.
I didn't do any big changes on server, other then upgraded to Coppermine 1.4.5.
Can someone please help me on this, I had to turn gallery offline  :'(

[blablabla]

I also had this error :

Template error
Failed to find block 'output_buffer'(#(<!-- BEGIN output_buffer -->)(.*?)(<!-- END output_buffer -->)#s) in :

        <tr>
                <td class="tableb" align="center">
                        <font size="3"><b>{MESSAGE}</b></font>
<!-- BEGIN file_line -->
                        <br />
                        <br />
                        {FILE_TXT}{FILE} - {LINE_TXT}{LINE}
<!-- END file_line -->

                        <br /><br />
                </td>
        </tr>

but it was gone when i refresh page :S

[Joachim Müller]

did you upgrade as suggested in the docs? Did you upgrade your theme as well? What version did you upgrade from? Post a link to your coppermine page.