seems that you have insufficent resources in your VPS. try the following command inside your VPS:
cat /proc/user_beancounters
that should produce some output like:
Version: 2.5
uid resource held maxheld barrier limit failcnt
231: kmemsize 345943 734774 2752512 2936012 0
lockedpages 0 0 32 32 0
privvmpages 1176 8123 49152 53575 0
shmpages 0 656 8192 8192 0
dummy 0 0 0 0 0
numproc 8 16 65 65 0
physpages 750 4840 0 2147483647 0
vmguarpages 0 0 6144 2147483647 0
oomguarpages 750 4840 6144 2147483647 0
numtcpsock 2 4 80 80 0
numflock 2 8 100 110 0
numpty 1 3 16 16 0
numsiginfo 0 3 256 256 0
tcpsndbuf 0 8912 319488 524288 0
tcprcvbuf 0 25656 319488 524288 0
othersockbuf 2228 7376 132096 336896 0
dgramrcvbuf 0 4276 132096 132096 0
numothersock 1 5 80 80 0
dcachesize 39520 76326 1048576 1097728 0
numfile 87 171 2048 2048 0
dummy 0 0 0 0 0
dummy 0 0 0 0 0
dummy 0 0 0 0 0
numiptent 10 10 128 128 0
have a look at the last column, if there are any numbers, other then 0 then you have to adjust the according parameter. i think you have to increase the socketbuffers.
hth,
mario.