Disk space overload? - 500 - Internal Server Error

[LotteB]

Dear forum,

i'm using Parallels Plesk, with the Parallels Power panel.

I woke up this morning with my mailbox full of these messages:

Out: 220 Domain.nl ESMTP Postfix
In: EHLO nvo-mail-ciit.ciit.netwok
Out: 250-Domain.nl
Out: 250-PIPELINING
Out: 250-SIZE 10240000
Out: 250-ETRN
Out: 250-STARTTLS
Out: 250-AUTH PLAIN DIGEST-MD5 LOGIN CRAM-MD5
Out: 250-ENHANCEDSTATUSCODES
Out: 250-8BITMIME
Out: 250 DSN
In: MAIL FROM:<mail@yahoo.com> SIZE=2613
Out: 452 4.3.1 Insufficient system storage
In: QUIT
Out: 221 2.0.0 Bye

For other details, see the local mail logfile

I figured my disk space was to full? So I logged in to my Plesk panel and deleted a few big files in various domains.
Then, all of a sudden, my Plesk went offline with this message:

500 - Internal Server Error

Now, I cant login to my Plesk panel.
My website's are running, but when i try to login to the ftp, webmail or backend it doesn't work.

Then, I logged in to my Power Panel (which is working fine).
I found out my Disk Space is 100% full.

Also, at the "System Service"-tab I found out these services are offline:
-CROND
-NAMED
-SMB

When I try to restart these services, it doesn't work.

Could anybody help me?
Is my next step to try and lower my Disk space? And if so, how do I do this without Plesk or FTP?

Kind regards,

Lotte van Breugel